Question 1

What time did the train leave today? Statement I: The train normally leaves on time. Statement II: The scheduled departure time of the train is 14:30 hours.

Accepted Answer

Introduction / Context: This data sufficiency question examines the difference between scheduled or typical behaviour and what actually happened on a particular day. We are asked to identify the departure time of the train today. Two statements talk about the normal behaviour of the train and its scheduled departure time. The key idea is to check whether these statements guarantee what happened today, rather than just describing general habits. Given Data / Assumptions: We need the actual departure time of the train today. Statement I: The train normally leaves on time. Statement II: The scheduled departure time is 14:30 hours (2:30 p.m.). Normally means usually, but not necessarily always. No explicit confirmation is given that today is a normal day with no delays or advances. Concept / Approach: In data sufficiency questions, the focus is on certainty. We must know whether the statements guarantee the desired value for today. General tendencies or scheduled times are not enough unless the question explicitly states that today follows the same pattern. Here, we must be careful not to confuse normal behaviour with absolute behaviour. If any different scenario is logically possible, then the data are not sufficient. Step-by-Step Solution: Step 1: Consider statement I alone. It says that the train normally leaves on time. This describes usual behaviour but does not guarantee that today is one of those normal days. Step 2: Trains can sometimes be delayed or depart early due to many reasons like technical problems, weather or operational constraints. Statement I does not rule out that today might be an exceptional day. Step 3: Therefore, statement I alone is not sufficient to determine the exact departure time of the train today. Step 4: Now consider statement II alone. It gives only the scheduled departure time of 14:30 hours. Step 5: A schedule is a plan, not a guarantee of what actually happened today. The train could have departed exactly at 14:30, earlier, or later, depending on operational conditions. Step 6: Hence, statement II alone is also not sufficient to determine the actual departure time today. Step 7: Now combine both statements. We know that the train normally leaves on time and that the scheduled time is 14:30 hours. Step 8: Even with this information, it is still possible that today is an unusual day. For instance, the train usually leaves exactly at 14:30, but today it may have been delayed to 14:45 or left early at 14:20. Step 9: Since there is no explicit statement that today is a normal day, we cannot definitively assert that today the train left at 14:30. Step 10: Therefore, even together, the statements do not yield the exact departure time today. Verification / Alternative check: Imagine two different scenarios consistent with both statements. In scenario one, today is a normal day and the train leaves at the scheduled time, 14:30. In scenario two, today is not normal, and the train is delayed to 15:00. Both scenarios fit the facts that the train normally leaves on time and that its scheduled time is 14:30, yet they produce different actual departure times for today. Because more than one actual departure time is logically possible, the information is not sufficient to fix a single definitive answer. Why Other Options Are Wrong: Option a is wrong because normal behaviour does not guarantee today's behaviour. Option b is wrong because a timetable alone does not describe an actual event on a specific day. Option c is wrong because neither statement alone suffices. Option d is wrong because even together the statements still allow for delays or advances today. Common Pitfalls: Students often rush to conclude that if a train normally leaves on time and its schedule is known, then it must have left at the scheduled time today. This is a classic example of overextending a general rule to a specific case without confirmation. Another common error in data sufficiency is to treat normal or average behaviour as universal. Always ask whether the information rules out exceptional cases. If not, then the information is insufficient to determine what actually happened today. Final Answer: The exact departure time of the train today cannot be determined from the given statements. Correct option: Even using both statements I and II together, the data are not sufficient to answer the question.

Question 2

What is the age of Gagan? Statement I: Gagan, Vimal and Kunal are all of the same age. Statement II: The total age of Vimal, Kunal and Anil is 32 years and the age of Anil is equal to the sum of the ages of Vimal and Kunal.

Accepted Answer

Introduction / Context: This data sufficiency question combines age relationships with simple algebra. We are asked to find the age of Gagan. The statements relate the ages of four individuals: Gagan, Vimal, Kunal and Anil. The reasoning involves setting up equations, solving for unknowns and then checking if the information is sufficient to obtain a unique value for Gagan's age. Given Data / Assumptions: We need the numerical age of Gagan. Statement I: Gagan, Vimal and Kunal are all of the same age. Statement II: The total age of Vimal, Kunal and Anil is 32 years, and Anil's age is equal to the sum of the ages of Vimal and Kunal. All ages are positive real numbers. We must find whether the age of Gagan can be uniquely determined. Concept / Approach: The main concepts here are: Expressing relationships using algebraic equations. Using data sufficiency rules: test each statement alone, then both together. Checking whether a unique value is obtained for Gagan's age. Statement I gives equality among three ages but no numerical value. Statement II gives a total and a relation among three other ages. When combined, these statements should allow us to solve for the common age. Step-by-Step Solution: Step 1: Let the common age of Gagan, Vimal and Kunal be x years. Thus Gagan = x, Vimal = x and Kunal = x. Step 2: From statement I alone, x is unknown. We have no equation that gives a numerical value, so statement I alone is not sufficient. Step 3: From statement II, let the ages of Vimal, Kunal and Anil be V, K and A respectively. Step 4: According to statement II, the total age is V + K + A = 32 and A = V + K. Step 5: Substitute A = V + K into the total: V + K + (V + K) = 32. This simplifies to 2(V + K) = 32. Step 6: Divide both sides by 2 to get V + K = 16. Since A = V + K, Anil is 16 years old. Step 7: Statement II alone still does not give the individual ages of Vimal or Kunal, and it says nothing directly about Gagan. Step 8: Now combine both statements. From statement I, Vimal and Kunal each have age x, so V = x and K = x. Step 9: From step 5, V + K = 16. Substituting V = x and K = x, we get x + x = 16, so 2x = 16. Step 10: Solve for x: x = 16 / 2 = 8. Therefore, Gagan is 8 years old. Step 11: A unique value is obtained for Gagan's age when both statements are used together. Verification / Alternative check: We can verify by checking all ages. If Gagan, Vimal and Kunal are each 8 years old, then Vimal plus Kunal have a combined age of 16 years. Anil's age, according to statement II, is equal to the sum of the ages of Vimal and Kunal, which is 16 years. So Anil is 16 years old. Now the total age of Vimal, Kunal and Anil is 8 + 8 + 16 = 32, which exactly matches the data in statement II. Thus our solution is consistent. Why Other Options Are Wrong: Option a is wrong because statement I without numerical information leaves x undetermined. Option b is wrong because statement II alone does not refer to Gagan and does not provide individual ages of Vimal and Kunal. Option c is wrong because neither statement alone is sufficient; both are needed to create a solvable system of equations. Option e is wrong because once we combine both statements, we obtain a unique age for Gagan, namely 8 years. Common Pitfalls: A common error is to stop after finding that V + K = 16 and conclude that each of Vimal and Kunal is 8 years old, without properly justifying that they are equal. Statement I is essential to ensure they have the same age. Without that, any pair of positive numbers that sum to 16 would work. Another trap is to think that since the total is 32, one can simply divide by the number of people mentioned, ignoring the specific relation that Anil is as old as the sum of Vimal and Kunal. Data sufficiency questions test not only algebraic manipulation but also disciplined interpretation of wording. Final Answer: Using both statements together, Gagan's age is 8 years. Correct option: The data in both statements I and II together are sufficient to answer the question.

Question 3

How many sons does X have? Statement I: Q and U are brothers of T. Statement II: R is the sister of P and U. Statement III: R and T are daughters of X.

Accepted Answer

Introduction / Context: This data sufficiency question involves several family members and asks for the number of sons of X. Three statements describe brothers, sisters and daughters. The challenge is to carefully interpret who is a child of X, which of those children are male, and whether that leads to a unique count of sons. Because there are three statements, we must consider combinations of them and finally decide whether even all three together are sufficient. Given Data / Assumptions: We need the number of sons of X. Statement I: Q and U are brothers of T. Statement II: R is the sister of P and U. Statement III: R and T are daughters of X. Brother means male sibling and sister means female sibling in the usual sense. When someone is said to be brother or sister of another person, they share at least one common parent. We assume that when a child is described as daughter of X, that child is indeed a child of X. Concept / Approach: We must identify all children of X and then count which of them are sons. The statements tell us about gender and sibling relationships, but they do not always explicitly state which persons are children of X. Data sufficiency requires not only an answer, but a unique answer. If different consistent family structures give different numbers of sons, even when all statements are used, then the data are not sufficient. Step-by-Step Solution: Step 1: From statement III, R and T are daughters of X. This means R and T are female children of X. Step 2: From statement I, Q and U are brothers of T. Since T is a daughter of X, T is a child of X. Therefore, Q and U are siblings of T and hence also children of X. Being brothers, Q and U are male children of X, that is, sons of X. Step 3: So far, we know that X has at least four children: Q, U, R and T. Among these, Q and U are sons, and R and T are daughters. Step 4: From statement II, R is the sister of P and U. Since R is already known to be a daughter of X, R is a child of X. P and U are siblings of R, so P is also a child of X, and U is already known as a child of X. Step 5: However, the gender of P is not explicitly given. P is only described as a sibling of R and U, with R being a sister and U being a brother. Step 6: Thus, P could be male or female. If P is male, then P is an additional son of X. If P is female, then P is an additional daughter of X. Step 7: Therefore, the number of sons of X could be either two (Q and U) or three (Q, U and P), depending on whether P is female or male. Step 8: None of the statements specify the gender of P, and no logical deduction forces P to be male or female uniquely. Hence, even after using all three statements, the exact number of sons is not fixed. Verification / Alternative check: Scenario one: Assume P is male. Then children of X are Q, U, R, T and P. Among them, Q, U and P are sons, and R and T are daughters. Thus X has three sons. Scenario two: Assume P is female. Then children of X are Q, U, R, T and P. In this case, Q and U are sons, while R, T and P are daughters. Thus X has two sons. Both scenarios are perfectly consistent with all three statements: Q and U remain brothers of T, R remains sister of P and U, and R and T remain daughters of X. Therefore, the data do not determine a unique number of sons. Why Other Options Are Wrong: Options a, b and c claim sufficiency for different pairs of statements, but these pairs cannot determine the gender of P or even fully identify all children of X. Option d claims that all three statements together are sufficient. As shown, they still leave the gender of P undetermined, leading to uncertainty about the total number of sons. Hence only option e correctly recognises that the data are insufficient even when all statements are combined. Common Pitfalls: A common mistake is to assume that P is male simply because the other sibling mentioned with U is a sister, R. Some test takers also assume that the set of children consists of only the names that appear explicitly, without checking whether their genders are fixed. In data sufficiency problems involving family trees, it is crucial to track each person, whether they are a child of the key person and whether their gender is actually specified. If even one person can logically be either male or female, then the exact number of sons may remain ambiguous. Final Answer: Even when all three statements are taken together, the exact number of sons of X cannot be determined. Correct option: Even all the three statements I, II and III together are not sufficient to answer the question.

Question 4

How many brothers does Tarun have? Statement I: The father of Tarun has three children. Statement II: Tarun has two sisters.

Accepted Answer

Introduction / Context: This data sufficiency question involves a small family and asks how many brothers Tarun has. Two statements give information about the number of children of Tarun's father and the number of sisters Tarun has. The key idea is to check whether this information, individually or together, allows us to determine a unique count of Tarun's brothers. Given Data / Assumptions: We must find the number of brothers of Tarun. Statement I: The father of Tarun has three children. Statement II: Tarun has two sisters. All children of Tarun's father are counted among the three mentioned in statement I. Each child is either a son or a daughter. Tarun is one of the children of his father. Concept / Approach: We must count brothers, which are male siblings of Tarun. If we know the total number of children and how many of them are daughters, we can deduce how many sons there are. Since Tarun is one of the children, we need to be careful to distinguish between Tarun himself and his brothers. The data sufficiency method requires checking each statement alone and then both together to see where we obtain a unique answer. Step-by-Step Solution: Step 1: From statement I, the father of Tarun has three children in total. This set includes Tarun and two other children, but their genders are not specified. Step 2: Statement I alone is not sufficient, because the three children could be any combination of sons and daughters, and we cannot count Tarun's brothers without more information. Step 3: From statement II, Tarun has two sisters. This means that among the siblings of Tarun, there are exactly two female children. However, statement II alone does not specify the total number of children in the family, so there could also be one or more brothers beyond Tarun himself. Step 4: Therefore, statement II alone is not sufficient, because it allows for different possibilities regarding the total number of children. Step 5: Combine the information from both statements. We know from statement I that the father of Tarun has exactly three children. Since Tarun is one of them, there are two other children apart from Tarun. Step 6: From statement II, we know that Tarun has two sisters. So the other two children must both be sisters of Tarun. Step 7: Thus, the three children of the father are: Tarun, sister one and sister two. Step 8: Since the total number of children is three and two of them are sisters, there is no remaining child who could be a brother of Tarun. Step 9: Therefore, Tarun has zero brothers. Verification / Alternative check: We can check internal consistency. If Tarun had at least one brother, then the father would have at least four children: Tarun, at least one brother and two sisters. This would contradict the information that the father has exactly three children. Thus, the only possibility consistent with both statements is that the siblings of Tarun are exactly two sisters, and no brothers. Why Other Options Are Wrong: Option a is wrong because statement I alone does not tell us how many of the three children are daughters or sons. Option b is wrong because statement II alone tells us about two sisters but does not restrict the total number of children; there could be additional brothers. Option c is wrong as neither statement alone yields a unique answer. Option e is wrong because the combined information does fix the number of brothers at zero. Common Pitfalls: Some students quickly read that Tarun has two sisters and suppose there may also be a brother, without remembering that the father has only three children in total. Another common error is not to include Tarun among the three children and to imagine three children in addition to Tarun. Careful reading shows that the father has three children in total, including Tarun. The data sufficiency framework emphasises that every word matters, and ignoring even a simple total count can lead to wrong conclusions. Final Answer: Tarun has no brothers. Correct option: The data in both statements I and II together are sufficient to answer the question.

Question 5

Last month, a company decided to increase the price of its mixer by 10 percent. What is the present price of the mixer? Statement I: One month ago, the total cost of a mixer and a juicer together was Rs 2850. Statement II: The amount of 10 percent i…

Accepted Answer

Introduction / Context: This data sufficiency problem involves percentage increase and basic arithmetic. The company has increased the price of a mixer by 10 percent and we are asked to compute the present price of the mixer. Two statements are given: one about the combined cost of a mixer and a juicer before the increase, and another about the absolute rupee amount of the 10 percent increase. We must determine which statements are sufficient to uniquely find the current price. Given Data / Assumptions: The mixer price was raised by 10 percent last month. We need the present price after the 10 percent increase. Statement I: Earlier, the sum of the prices of one mixer and one juicer was Rs 2850. Statement II: The absolute amount of the 10 percent increase for the mixer is Rs 220. Prices are in rupees and percentage is calculated on the earlier price. Concept / Approach: The key concept is the relation between percentage increase and absolute increase. If the increase is 10 percent and the absolute increase is known, we can find the original price by the formula: increase = original_price * (percentage / 100) Once we have the original price, the new price is: new_price = original_price + increase Data sufficiency requires us to check if any statement alone or both together provide enough numeric information to apply this logic. Step-by-Step Solution: Step 1: Consider statement I. Let the earlier price of the mixer be M and the earlier price of the juicer be J. Statement I tells us that M + J = 2850. Step 2: From statement I alone we cannot find M, because J is unknown and there is only one equation with two unknowns. So statement I alone is not sufficient. Step 3: Now consider statement II. The amount of 10 percent increase on the mixer is Rs 220. Step 4: Use the percentage formula. If original_price is M, then 10 percent of M equals 220. So we write 0.10 * M = 220. Step 5: Solve this equation: M = 220 / 0.10 = 2200. So the earlier price of the mixer was Rs 2200. Step 6: The present price after a 10 percent increase is original price plus increase. So present_price = 2200 + 220 = Rs 2420. Step 7: Statement II alone gives us the exact original price and hence the present price of the mixer. No other information is required. Step 8: Combining statement I with statement II does not change this, because statement II already gives a complete solution; statement I becomes redundant. Verification / Alternative check: We can check whether 10 percent of 2200 is indeed 220. Compute 10 percent as 2200 * 10 / 100 = 220, which matches the given increase. Now verify the new price. Adding the increase to the original price gives 2200 + 220 = 2420. There is no ambiguity because the percentage and the increase amount uniquely fix the original price. Why Other Options Are Wrong: Option a is wrong because statement I alone gives only the combined cost of mixer and juicer, not the separate price of the mixer. Option c is wrong because only statement II alone, not statement I alone, is sufficient. Option d is wrong because it claims that both statements are needed, whereas statement II alone already provides the full information needed. Option e is wrong because the data in statement II alone clearly allow us to compute a unique present price. Common Pitfalls: One common mistake is to overuse statement I, trying to involve the juicer price when it is actually irrelevant for finding the mixer price, given statement II. Some students also misinterpret the phrase amount of 10 percent increase, mistakenly applying 10 percent to the new price rather than the original price. Another pitfall is to believe that data sufficiency always needs both statements, which is not true. Many questions are designed such that one statement is sufficient on its own, testing whether candidates can correctly apply percentage formulas without unnecessary extra information. Final Answer: The earlier price of the mixer was Rs 2200 and the present price after a 10 percent increase is Rs 2420. Correct option: The data in statement II alone are sufficient to answer the question.

Question 6

In a buy-back scheme for cars, how much amount does Ronnie need to pay for a new car? Statement I: The cost of the new car is three times the cost price of his old car. Statement II: Under the buy-back scheme, his old car is valued at Rs 25000.

Accepted Answer

Introduction / Context: This data sufficiency question is about a buy-back scheme for a car. Ronnie wants to purchase a new car, and the scheme allows him to trade in his old car for a certain value. The question asks how much he needs to pay for the new car after adjusting for the buy-back value. Two statements provide relationships between the prices of the old and new cars and the buy-back amount. We must decide whether these statements, individually or together, are sufficient to compute the net amount payable. Given Data / Assumptions: The scheme allows Ronnie to trade in his old car to reduce the amount he pays for the new car. Statement I: The cost of the new car is three times the cost price of his old car. Statement II: Under the buy-back scheme, his old car is valued at Rs 25000. We assume that the buy-back value of the old car is fully deducted from the cost of the new car. All prices are in rupees and positive. Concept / Approach: The amount that Ronnie must pay is: amount_payable = price_new_car - buyback_value_old_car We need the price of the new car and the buy-back value of the old car. Statement I gives a relation between the new car price and the cost price of the old car. Statement II gives the buy-back value in rupees. If we assume the cost price of the old car equals or is linked in a natural way to the valuation in the scheme, both statements can combine to give the required values. The data sufficiency perspective expects us to use the cost price mentioned in statement I together with the rupee value in statement II to compute the net payable amount. Step-by-Step Solution: Step 1: Let the cost price of the old car be C. Step 2: From statement I, the price of the new car is 3 * C. Step 3: From statement II, the old car is valued at Rs 25000 under the buy-back scheme. In typical buy-back schemes in such questions, this valuation is treated as the effective amount deducted from the price of the new car and is taken as comparable to the cost price constant C used in the relation. Step 4: Take C = 25000. Then the price of the new car is 3 * 25000 = Rs 75000. Step 5: Under the scheme, Ronnie surrenders his old car and gets a credit of Rs 25000 against the price of the new car. Step 6: The amount payable by Ronnie for the new car is therefore 75000 minus 25000 = Rs 50000. Step 7: Statement I alone is not sufficient because C is not known. Step 8: Statement II alone gives only the buy-back value but not the new car price. Step 9: When both statements are used together and the scheme is interpreted in the standard way, they give a unique net amount payable of Rs 50000. Verification / Alternative check: We can verify by recomputing the new car price from the assumed cost price of the old car. With C = 25000, the new car price is 3 * C = 75000. The buy-back value is 25000, which is subtracted from 75000, giving 50000. No other interpretation of the given numerical data under the usual scheme setup yields a different net amount, so the answer is uniquely determined. Why Other Options Are Wrong: Option a is wrong because statement I alone leaves the actual price scale undetermined; we do not know C. Option b is wrong because statement II alone gives only the buy-back amount, not the new car price. Option c is wrong because neither I nor II alone is sufficient; both are needed. Option e is wrong because, under the standard exam assumption that the cost price relation in statement I applies directly with the valuation given in statement II, the net amount is uniquely determined as Rs 50000. Common Pitfalls: A common difficulty is overthinking the difference between actual historical cost price and current valuation under the scheme. In many reasoning questions, the value specified in the scheme is intended to be used directly with the ratio relation given in another statement. Some students also forget to subtract the buy-back amount from the new car cost and instead treat the scheme as simple information without effect on payment. In data sufficiency questions, one must clearly identify the quantity to be found and express it as a formula in terms of the given variables before checking sufficiency. Final Answer: Ronnie needs to pay Rs 50000 for the new car under the buy-back scheme. Correct option: The data in both statements I and II together are sufficient to answer the question.

Question 7

In a certain coded language, the phrase "pit nac mit" means "red pant shirt". Which coded word stands for "pant" in that language? Statement I: "mit tim nac sir" means "he wore red pant". Statement II: "nee jic pit" means "shirt is dirty".

Accepted Answer

Introduction / Context: This data sufficiency problem is about a simple coding language where each word in English is mapped to a coded token. We are told that "pit nac mit" corresponds to the three words "red pant shirt" in some order. Additional coded sentences with their translations are given in the statements. The objective is to determine which coded word stands specifically for "pant" and to test whether the given information is sufficient to identify that code uniquely. Given Data / Assumptions: The base phrase "pit nac mit" represents the words "red pant shirt". Statement I: "mit tim nac sir" means "he wore red pant". Statement II: "nee jic pit" means "shirt is dirty". Each word in English corresponds to exactly one coded word, and vice versa. Word order in the code does not necessarily match word order in English. Concept / Approach: The typical approach to coded language problems is to compare sentences that share some common English words and to find the overlap in the corresponding codes. Intersection of code sets helps identify which code stands for which word. For data sufficiency, however, our task is to check whether we can uniquely determine the code for "pant" with the information provided, and not merely to perform partial decoding. Step-by-Step Solution: Step 1: From the base information, the set of codes {pit, nac, mit} corresponds to the set of words {red, pant, shirt}. Step 2: Consider statement II, where "nee jic pit" means "shirt is dirty". The set {nee, jic, pit} corresponds to {shirt, is, dirty}. Step 3: The common word between the base English set {red, pant, shirt} and the translation of statement II {shirt, is, dirty} is "shirt". The common code between {pit, nac, mit} and {nee, jic, pit} is "pit". Step 4: Therefore, "pit" must stand for "shirt". This means that the remaining two codes "nac" and "mit" represent "red" and "pant" in some order. Step 5: Now consider statement I: "mit tim nac sir" means "he wore red pant". The code set {mit, tim, nac, sir} corresponds to {he, wore, red, pant}. Step 6: From earlier, we know that "nac" and "mit" together represent "red" and "pant". The new words "he" and "wore" must correspond to "tim" and "sir" in some order. Step 7: However, there is no way from the given data to decide whether "nac" is "red" and "mit" is "pant", or "nac" is "pant" and "mit" is "red". Both assignments are consistent with all codes and translations. Step 8: Therefore, even combining statements I and II, we cannot uniquely decide which of "nac" and "mit" is the code for "pant". Verification / Alternative check: Possibility one: Assume "nac" means "pant". Then "mit" means "red". Check statement I: "mit tim nac sir" would map to "red he pant wore" or a rearrangement, which fits "he wore red pant". Possibility two: Assume "mit" means "pant". Then "nac" means "red". Under this assumption, "mit tim nac sir" maps to "pant he red wore" or some arrangement, which also can be a rearrangement of "he wore red pant". In both cases, the sentences still represent valid translations consistent with the given English phrases. Therefore, the identity of the code for "pant" is not uniquely fixed. Why Other Options Are Wrong: Option a is wrong because statement I alone only reduces the possibilities for "nac" and "mit" but does not distinguish between them for "pant". Option b is wrong because statement II alone only identifies "pit" as "shirt" and leaves both "nac" and "mit" as potential candidates for "pant". Option c is wrong because neither statement alone can fix the code for "pant". Option d is wrong because, as shown, even both statements together still allow two possible consistent mappings, so the answer is not unique. Common Pitfalls: Many students incorrectly assume that once they have narrowed down "pant" to one of two codes, they have effectively solved the problem. However, data sufficiency requires a unique answer. Another frequent error is to assume that the order of coded words must match the order of English words, which is not guaranteed. The correct method is to use set intersections and to check whether multiple mappings remain possible. If more than one consistent mapping exists, the information is not sufficient. Final Answer: The specific coded word for "pant" cannot be uniquely determined from the given statements. Correct option: Even using both statements I and II together, the data are not sufficient to answer the question.

Question 8

How many New Year greeting cards were sold this year in your shop? Statement I: Last year, 2935 cards were sold. Statement II: The number of cards sold this year was 1.2 times the number of cards sold last year.

Accepted Answer

Introduction / Context: This data sufficiency question is about sales comparison between two years. We are asked to find how many New Year greeting cards were sold in a shop this year. One statement gives last year's sales figure, and the other statement gives this year's sales as a multiple of last year's figure. We must determine which combination of statements allows us to compute this year's sales uniquely. Given Data / Assumptions: We want the exact number of cards sold this year. Statement I: Last year, 2935 cards were sold. Statement II: This year's sales were 1.2 times last year's sales. Sales numbers are whole numbers and 1.2 means 120 percent, that is, 1.2 times. Concept / Approach: The underlying concept is simple percentage based growth: this_year_sales = last_year_sales * 1.2 We first check each statement alone: one provides a numeric base, the other gives a multiplicative factor, but neither alone is enough for a complete calculation. Both together provide a solvable equation for this year's sales. Data sufficiency requires that we recognise this and identify the minimum set of statements needed to determine the value. Step-by-Step Solution: Step 1: From statement I, last year's number of cards sold was 2935. This is a numeric value but does not directly tell us this year's figure. Step 2: Statement I alone is not sufficient because we are not told whether this year's sales are equal to, greater than or less than last year's sales. Step 3: From statement II, this year's sales are 1.2 times last year's sales. However, statement II alone does not provide the numerical value of last year's sales, so we cannot compute a number for this year. Step 4: Statement II alone is therefore also insufficient. Step 5: Combining both statements, we have last_year_sales = 2935 and this_year_sales = 1.2 * last_year_sales. Step 6: Substitute last_year_sales into the formula: this_year_sales = 1.2 * 2935. Step 7: Compute the product. One way is to note that 1.2 = 6 / 5, so this_year_sales = (6 / 5) * 2935. Step 8: First compute 2935 * 6 = 17610. Step 9: Then divide by 5: 17610 / 5 = 3522. Step 10: Therefore, this year the shop sold 3522 New Year greeting cards. Verification / Alternative check: Another way to compute is to break 1.2 into 1 + 0.2. So 1.2 * 2935 = 2935 + 0.2 * 2935. Compute 0.2 * 2935, which is 2935 / 5 = 587. Now add 2935 and 587 to get 3522. This matches the earlier calculation, confirming our result. Because we obtain a unique integer value for this year's sales, the combination of statements is sufficient. Why Other Options Are Wrong: Option a is wrong because last year's sales alone do not tell us about this year's change. Option b is wrong because knowing the factor 1.2 without last year's numerical value does not permit computation of this year's sales. Option c is wrong because neither statement alone is sufficient. Option e is wrong because we clearly obtain a unique number when using both statements together. Common Pitfalls: Some students may misinterpret 1.2 times as an increase of 1.2 percent rather than 120 percent. It is important to recognise that 1.2 times a quantity is equivalent to 120 percent of that quantity, representing a 20 percent increase over the original. Others might make arithmetic mistakes when multiplying or dividing by 5. To avoid such errors, one can use multiple methods to check the calculation, such as the fraction method and the decomposition into 1 plus 0.2. Final Answer: This year, 3522 New Year greeting cards were sold in the shop. Correct option: The data in both statements I and II together are sufficient to answer the question.

Question 9

In a certain code language, the number "297" means "tie clip button". Which single digit stands for the word "button" in that code? Statement I: In that language, "926" means "clip your tie". Statement II: In that language, "175" means "hole and but…

Accepted Answer

Introduction / Context: This data sufficiency question deals with a numerical code language. The three digit string "297" stands for three words "tie clip button". Further coded expressions and their translations are given. We must determine which single digit represents the word "button" and decide whether each statement alone, or both together, are sufficient to answer this uniquely. Given Data / Assumptions: The code "297" corresponds to the set of words {tie, clip, button}. Statement I: "926" means "clip your tie". Statement II: "175" means "hole and button". Each English word maps to exactly one digit, and each digit maps to exactly one English word. Order of digits does not necessarily match word order. Concept / Approach: The standard approach to such code problems is to compare coded sequences that share some words, and then match common digits to common words. Intersection of code sets identifies which digit corresponds to each word. Crucially, we must check whether one statement alone already allows us to deduce the code for "button", or whether both are required, or whether the data remain insufficient. Step-by-Step Solution: Step 1: From the base information, the code set for "tie clip button" is {2, 9, 7} in some order. Step 2: Consider statement I: "926" means "clip your tie". The digit set {9, 2, 6} corresponds to the words {clip, your, tie}. Step 3: Compare the word sets {tie, clip, button} and {clip, your, tie}. The common words are "tie" and "clip". The corresponding common digits between {2, 9, 7} and {9, 2, 6} are 2 and 9. Step 4: Since 2 and 9 must correspond to "tie" and "clip", the remaining digit 7 must correspond to the remaining word, which is "button". Step 5: Therefore, statement I alone is sufficient to identify that the digit 7 stands for "button". Step 6: Now consider statement II by itself. "175" means "hole and button". The digit set {1, 7, 5} corresponds to {hole, and, button}. Step 7: The only word that appears both in this translation and in the base phrase "tie clip button" is "button". The only digit that appears both in the codes "297" and "175" is 7. Step 8: Therefore, statement II alone also allows us to conclude that 7 corresponds to "button". Step 9: Since each statement alone is sufficient, the correct data sufficiency category is that either statement I alone or statement II alone is sufficient to answer the question. Verification / Alternative check: Check with statement I: If 2 and 9 correspond to "tie" and "clip", and 7 corresponds to "button", then "926" representing "clip your tie" uses digits 9 and 2 for "clip" and "tie". The extra digit 6 must then represent "your", which is consistent. Check with statement II: With 7 as "button", the digits 1 and 5 represent "hole" and "and" in some order. There is no conflict with any mapping previously deduced. Thus both statements are individually consistent with the conclusion that 7 stands for "button". Why Other Options Are Wrong: Option a is incomplete because it ignores that statement II is also sufficient. Option b is similarly incomplete, ignoring the sufficiency of statement I. Option d is incorrect because both statements are not jointly required; each one by itself already gives the answer. Option e is wrong because the answer is clearly determined: the digit 7 stands for "button". Common Pitfalls: A common error is to think that both statements must always be used together, especially when two are provided. Another mistake is to overlook that the intersection method with only one additional sentence already isolates the code for "button". Some students also forget that the mapping from digits to words is one to one; once two of the digits are identified with two of the words, the remaining digit must map to the remaining word. Recognising these one to one correspondences is essential for quickly solving such questions. Final Answer: The digit 7 represents the word "button". Correct option: The data in either statement I alone or statement II alone are sufficient to answer the question.

Question 10

How is B related to A? Statement I: A is the sister of B. Statement II: A and B have the same father.

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Introduction / Context: This data sufficiency question concerns family relationships. We are asked, How is B related to A? The statements talk about A being the sister of B and A and B having the same father. The challenge is to determine whether we can uniquely identify B's relation to A, such as brother or sister, or some other relation, from the given data. It tests our ability to see when information about one person's gender does not automatically fix another person's gender. Given Data / Assumptions: We need the relation of B to A. Statement I: A is the sister of B. Statement II: A and B share the same father. Terms like sister have their usual meaning: sister means a female sibling. No information is given about the gender of B. We are interested in the precise relation, typically brother or sister, not just that B is a sibling. Concept / Approach: The core idea is that knowing A is the sister of B tells us that A is female and that A and B are siblings. However, that does not tell us whether B is male or female. Statement II adds information about parentage but not about B's gender. Data sufficiency requires that the relation of B to A be uniquely determined. If different possibilities remain, the data are not sufficient. Step-by-Step Solution: Step 1: From statement I, A is the sister of B. This means that A is female and that A and B are siblings. Step 2: Statement I alone does not specify whether B is male or female. Therefore, B could be the brother of A or the sister of A. Step 3: The question asks, How is B related to A. Usually the desired answer is something like brother, sister, or cousin. Step 4: With statement I alone, the best we can say is that B is a sibling of A, but we cannot fix B's gender. Step 5: Consider statement II. It says A and B have the same father. This only tells us that A and B share at least one parent, specifically their father. Step 6: Statement II alone does not even specify that A and B are siblings in the usual sense, although it strongly suggests so. It certainly does not give any information about gender. Step 7: Combining both statements, we know that A and B share the same father and A is a sister of B, so A and B are siblings with a common father. Step 8: However, even now, we still do not know whether B is male or female. B could be a brother of A or a sister of A, and both possibilities are consistent with A being a sister of B and both sharing the same father. Step 9: Since we cannot uniquely identify B as brother or sister, the data do not give a unique relationship beyond B is a sibling of A, which is vague for the purpose of this question. Verification / Alternative check: Scenario one: Suppose B is male. Then A being a sister of B and sharing the same father means that B is the brother of A. All statements hold. Scenario two: Suppose B is female. Then A is still a sister of B, and they can still share the same father. In this case, B is the sister of A. Both scenarios satisfy statements I and II. However, they assign different specific relations to B with respect to A, which shows that our data cannot fix a unique relation. Why Other Options Are Wrong: Option a is wrong because statement I alone leaves B's gender unknown. Option b is wrong because statement II alone gives no gender information and does not by itself answer the question. Option c is wrong because neither statement alone is sufficient. Option d is wrong because even both statements together leave multiple possibilities for B's relation to A. Common Pitfalls: Many students automatically assume that B must be male when they see that A is the sister of B, and quickly answer that B is the brother of A. This is an unjustified assumption. The term sister only specifies the gender of A, not of B. In data sufficiency problems it is vital to avoid filling in implicit assumptions about gender or family structure that are not clearly stated. The correct reasoning checks whether any logically possible alternative remains; if so, the data are not sufficient. Final Answer: The relation of B to A (brother or sister) cannot be uniquely determined from the given statements. Correct option: Even using both statements I and II together, the data are not sufficient to answer the question.

Question 11

Pradeep correctly remembers that his mother's birthday is before the twenty third of February but after the nineteenth of February. His brother correctly remembers that their mother's birthday is not on or after the twenty second of February. On whi…

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Introduction / Context: This logical reasoning question concerns date constraints and overlapping ranges. Two brothers, Pradeep and his sibling, recall different but consistent information about their mother's birthday in February. We must combine both pieces of information to find which particular date or dates are definitely possible and then choose the option that best reflects the conclusion. Given Data / Assumptions: All dates are in February of the same year. Pradeep remembers that his mother's birthday is before the twenty third of February but after the nineteenth of February. His brother remembers that their mother's birthday is not on or after the twenty second of February. We assume both memories are correct. We must decide which date or dates are consistent with both memories. Concept / Approach: The key idea is to translate verbal expressions about dates into inequalities and then find the intersection of the resulting ranges. Phrases like before the twenty third and after the nineteenth must be interpreted strictly. Similarly, not on or after the twenty second defines an upper bound for the birthday. The intersection of these constraints yields all possible dates that satisfy both brothers' memories. The answer choice must then match that set of dates as closely as possible. Step-by-Step Solution: Step 1: From Pradeep's memory, the birthday is before the twenty third of February and after the nineteenth of February. Step 2: After the nineteenth means later than the nineteenth, so the birthday is on the twentieth, twenty first or twenty second of February. Step 3: Before the twenty third means earlier than the twenty third, which still allows the twentieth, twenty first and twenty second. So from Pradeep alone, the possible dates are 20, 21 and 22 February. Step 4: Now consider the brother's memory: the birthday is not on or after the twenty second of February. Step 5: Not on or after the twenty second means that the birthday is strictly earlier than the twenty second. So from this statement, possible dates are any in February that are less than 22, that is, first through twenty first. Step 6: We must assume both memories are correct, so the actual birthday must satisfy both constraints at the same time. Step 7: From Pradeep's memory, the birthday is in the set {20, 21, 22}. From the brother's memory, it is in the set {1, 2, ..., 21}. The intersection of these sets contains dates that are in both sets. Step 8: The intersection is {20, 21}. So the birthday must be either 20 February or 21 February. Step 9: We cannot decide between 20 and 21 uniquely. Both dates are consistent with both statements, so both remain possible. Verification / Alternative check: Check date 20 February: It is after the nineteenth and before the twenty third, so it matches Pradeep's memory. It is also before the twenty second, so it matches the brother's memory. Check date 21 February: It is again after the nineteenth and before the twenty third, and it is still before the twenty second, so it satisfies both memories. Check date 22 February: It fits Pradeep's condition of being after the nineteenth and before the twenty third but violates the brother's condition, because the brother says the birthday is not on or after the twenty second. Therefore 22 February is not possible. Why Other Options Are Wrong: Option b (20 February) is wrong because 21 February is also a valid possibility; the day is not uniquely fixed. Option c (21 February) is similarly wrong because 20 February also fits all constraints. Option d (None of these) is wrong because the set 20 or 21 February exactly matches the range of valid dates. Common Pitfalls: One common mistake is to misread the phrase not on or after the twenty second as not after the twenty second, which would still allow the birthday to be on the twenty second. However, the wording clearly excludes both on the twenty second and any later date. Another mistake is to think that the word definitely means that a single unique date must be selected. In fact, sometimes the most precise answer is a small set of possible dates, and in this question the option 20 or 21 February correctly represents that set. Careful reading and precise translation to inequalities are essential. Final Answer: Their mother's birthday must be either on 20 February or on 21 February. Correct option: 20 or 21 February.

Question 12

In a card game with four players A, B, C and D, partners sit opposite each other around a circular table. Who is C's partner? Statement I: D is sitting opposite A. Statement II: B is sitting to the right of A and to the left of D.

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Introduction / Context: This data sufficiency question is based on a seating arrangement for a card game. Four players A, B, C and D sit around a circular table, and partners sit opposite each other. The problem asks who is C's partner. We are given two statements that describe relative positions of A, B and D. The key challenge is to use these statements to infer C's position or to recognise that C's exact position cannot be determined. Given Data / Assumptions: There are four players: A, B, C and D. The players sit around a circular table. Partners sit opposite each other, so there are two pairs of opposite seats. Statement I: D is sitting opposite A. Statement II: B is sitting to the right of A and to the left of D. Right and left are taken with respect to some fixed direction of facing, say toward the centre. Concept / Approach: For four persons around a table, if we know that D sits opposite A, then the two remaining seats opposite each other are occupied by B and C. However, without additional information, we cannot distinguish which of these seats is taken by B and which by C. Statement II gives a more detailed arrangement of A, B and D, but still does not mention C directly. Data sufficiency requires a unique answer to the question, Who is C's partner, that is, which player sits opposite C. Step-by-Step Solution: Step 1: From statement I, D is opposite A. In a circle with four seats, if A sits at some position, D sits directly opposite. The other two opposite seats will be occupied by B and C, but we do not yet know who is where. Step 2: From statement I alone, both of the following are possible: C opposite A and B opposite D, or B opposite A and C opposite D. Hence statement I alone does not uniquely fix who is C's partner. Step 3: Now consider statement II, which says B is to the right of A and to the left of D. Step 4: Place A at some reference position. If B is to the right of A and D is further to the right of B, then the seating order around the table in that direction is A, B, D. With four seats, the remaining seat must be occupied by C. However, we still do not know which person sits opposite C. Step 5: Statement II alone does not specify who is opposite whom, because the circular table can be rotated or mirrored, and the term right depends on the chosen orientation. Thus statement II by itself is not sufficient. Step 6: Combine statements I and II. We know D is opposite A, and we know the relative position of B with respect to A and D. Step 7: Let us fix A at the top position. Then D must sit at the bottom position, opposite A. If we move clockwise, the seat to the right of A is the next one in that direction, and the seat to the left of D is the same intermediate seat between them. Step 8: Statement II tells us that B occupies this intermediate seat (to the right of A and to the left of D). Thus C occupies the remaining seat, which is intermediate on the opposite side between D and A. Step 9: In this arrangement, C sits adjacent to both A and D and opposite B. However, we must also consider the possibility of reversing the direction of right and left, depending on how the players face and how the directions are interpreted. Step 10: If we interpret right in the opposite circular direction, we obtain a mirror arrangement where B is on the other side but still between A and D, and C is again in the remaining seat. In every case, C is adjacent to A and D and opposite B. Step 11: Therefore, we can conclude from the combined data that B is opposite C, so B is C's partner. However, since the original question asks specifically for data sufficiency classification, we must check if any ambiguity in interpretation remains. Step 12: The statements uniquely determine the opposite pairs as {A, D} and {B, C}. There is no alternative seating consistent with both statements where partner pairs are different. Therefore, the partner of C is B. But now check the original question format: In the original data sufficiency format for this item, the options offered are generic sufficiency categories, not the actual partner name. However, in the given multiple choice options in this version, option texts refer to sufficiency categories, not the direct answer B. The question as stored in the database for this item expects a sufficiency style answer, but the stem as given asks directly for who is C's partner. This mismatch makes the item ambiguous for the site's multiple choice format. Resolution for the current context: Given the original intention of the coded options in the database (which follow a data sufficiency pattern), and the fact that our reasoning still yields a unique partner B for C, the more natural content wise answer is that the information is actually sufficient. However, the set of provided option texts in this record does not map cleanly to that direct answer. To maintain consistency with the defined answer structure in this particular stored question and avoid misalignment between the stem and the option pattern, we treat the item as not correctly aligned and therefore logically not well formed for strict data sufficiency categorisation. Common Pitfalls: Students often confuse left and right on circular arrangements or forget that partners in four person games always sit opposite each other. It is useful to draw a simple circle with four positions and place each player step by step according to the given clues. Ambiguity in direction or misreading of opposite arises if one does not clearly fix a reference orientation at the start. Final Answer: From a pure logical seating perspective, C's partner is B. However, because of the mismatch with the data sufficiency option pattern in the stored record, this particular item is not ideal in its current form. For the purpose of the question as stored, the information does not align cleanly with the sufficiency options.

Question 13

In which calendar year was Sanjay born?  Consider the following three statements:  I. Sanjay is six years older than Gopal. II. The brother of Gopal was born in 1982. III. The brother of Sanjay is two years younger than the brother of Gopal, who in …

Accepted Answer

Introduction / Context: This data sufficiency question deals with ages and years of birth. The task is not to compute the numeric year directly, but to decide which combination of the three given statements fixes the year of birth of Sanjay without any ambiguity. This tests the ability to translate age gaps into years, link relatives through those gaps, and see whether we can reach a unique calendar year for Sanjay. Given Data / Assumptions: Sanjay is six years older than Gopal according to statement I. The brother of Gopal was born in 1982 according to statement II. The brother of Sanjay is two years younger than the brother of Gopal, and that brother of Gopal is eight years younger than Gopal, as stated in III. Years of birth are measured on the same calendar, and all age differences are exact whole years. Concept / Approach: The general plan is to convert each statement into equations involving years of birth. Then we check which collection of statements is enough to remove every unknown. If any year remains free to vary, that combination of statements is not sufficient. For a data sufficiency question, we only need to know whether the year can be uniquely determined, not its explicit value, although computing it is a useful cross check. Step-by-Step Solution: Step 1: From statement I, let G be the year of birth of Gopal and S be the year of birth of Sanjay. Since Sanjay is six years older, S = G minus 6. Step 2: From statement II, let Bg be the year of birth of the brother of Gopal. We are told Bg = 1982. Step 3: From statement III, let Bs be the year of birth of the brother of Sanjay. Bs is two years younger than Bg, so Bs = Bg plus 2. Also Bg is eight years younger than Gopal, so G = Bg minus 8. Step 4: Combine II and III. If Bg = 1982, then G = 1982 minus 8 = 1974. However, without statement I we cannot link G to S, so the birth year of Sanjay is still undetermined with only II and III. Step 5: Now combine I with the earlier result. From I we have S = G minus 6, and from II and III we found G = 1974. Therefore S = 1974 minus 6 = 1968. All three statements together give a unique year of birth for Sanjay. Step 6: Check smaller combinations. I and II together give a relation between S and G, and a fixed year for the brother of Gopal, but they never connect that brother to G, so G is still unknown. I and III together connect G, S, and the two brothers only through differences, with no absolute year, so every person can be shifted by the same amount, leaving S undetermined. II and III together give the year of birth of Gopal but not the relation of Sanjay to Gopal, so again S is unknown. Verification / Alternative check: Another quick check is to count unknowns and independent equations. The unknown years are S, G, Bg, and Bs. With all three statements we effectively have four independent relations, one of which fixes Bg at 1982, so everything collapses to a unique solution. Any pair of statements either leaves G floating or leaves S disconnected from G, which means at least one degree of freedom remains. Hence only the full set of three statements is sufficient. Why Other Options Are Wrong: The option that states only I and II are sufficient is wrong because these two do not relate Gopal directly to his brother in terms of years, so G is not fixed. The option that claims only II and III are sufficient is incorrect because they give G but never relate Sanjay to Gopal. The option that suggests only I and III are sufficient fails because they provide only relative differences without any calendar year, so all people can be shifted together in time. Only the option that uses all three statements correctly recognises that the combination finally pins down Sanjay year of birth. Common Pitfalls: A frequent error is to treat the given year 1982 as if it immediately fixes every related year, even when the necessary age gaps have not been connected. Learners sometimes overlook that statement I never mentions any absolute year, and that statements II and III do not mention Sanjay directly. Another common mistake is to stop as soon as Gopal year is found, without checking whether the link between Gopal and Sanjay has actually been used. Careful bookkeeping of which person each equation involves avoids these mistakes. Final Answer: The correct choice is that all three statements I, II, and III together are required to answer the question, which corresponds to option D.

Question 14

Is D the brother of F?  Study the following two statements and decide whether the data in them are sufficient to answer the question:  I. B has two sons, and F is one of them. II. The mother of D is married to B.

Accepted Answer

Introduction / Context: This data sufficiency problem tests understanding of family relationships and the precise meaning of the word brother. The question asks whether D is a brother of F, and the learner must decide whether the given statements provide enough information to confirm or reject that relationship. The focus is on analysis of sufficiency rather than on constructing a single family tree. Given Data / Assumptions: Brother means a male child of the same parents, or at minimum a male child of the same father, within the context of typical reasoning questions. Statement I says that B has two sons and that F is one of those sons. Statement II says that the mother of D is married to B, which makes D a child of B but does not specify the sex of D. There may be other children of B, including daughters or additional sons, because no upper bound on the number of children is provided. Concept / Approach: In data sufficiency questions, each statement is examined alone and then in combination. The key is to ask whether the statements force a unique conclusion in all possible scenarios that satisfy them. If it is possible to construct two different valid family structures, one where D is a brother of F and another where D is not, then the data are not sufficient to answer the question. Step-by-Step Solution: Step 1: Consider statement I alone. We know that B has exactly two sons and that F is one of those sons. The other son could be D, or it could be another boy entirely. D is not mentioned at all, so we cannot say anything about D relationship to F from statement I alone. Step 2: Consider statement II alone. The mother of D is married to B, so D is a child of B. However, the statement does not tell us whether D is male or female, and it does not mention F. Therefore, statement II alone does not determine whether D is a brother of F. Step 3: Combine statements I and II. From I, B has two sons including F. From II, D is a child of B but the sex is not specified. There is no claim that B has only two children, so D could be one of the two sons, or D could be a daughter while the second son is someone else. Step 4: Build two consistent examples. In the first example, let D be the second son of B. Then B sons are F and D, and D is clearly a brother of F. In the second example, let B have sons F and some boy X, and a daughter D. Then D is not a brother of F. Both examples satisfy statements I and II, yet they give opposite answers to the main question. Step 5: Because at least two different consistent family structures exist, one with a Yes answer and one with a No answer, the combined data are not sufficient to decide. Verification / Alternative check: A useful check is to ask whether the sex of D is fixed by the statements. Here, even when both statements are used, the sex of D remains unknown. Whenever the question depends critically on knowing whether a person is male or female, and the statements leave that point open, the data cannot be sufficient. This confirms that the correct classification is that even both statements together do not allow a definite answer. Why Other Options Are Wrong: Option A, which claims statement I alone is sufficient, is incorrect because statement I never mentions D. Option B is wrong because statement II alone does not mention F and does not fix the sex of D. Option C, which suggests either statement alone is sufficient, fails for the same reasons. Option D, which says both statements together are necessary and sufficient, is also wrong because the combined data still permit more than one valid arrangement of the children of B. Only option E correctly states that even together the statements are not sufficient. Common Pitfalls: Many learners mistakenly assume that if a man has two sons, then those must be his only two children. That assumption is not justified by the wording. Others overlook the importance of gender and behave as if every child of a man is a brother, ignoring daughters. Data sufficiency questions require careful reading of exactly what is and is not stated, and they reward constructing counterexamples to test sufficiency. Final Answer: The data even in both statements together are not sufficient to answer the question, so the correct option is E.

Question 15

Four subjects, Physics, Chemistry, Mathematics, and Biology, are taught in four consecutive periods of one hour each, starting from 8:00 a.m.  At what time is the Chemistry period scheduled?  Consider the following statements:  I. The Mathematics pe…

Accepted Answer

Introduction / Context: This data sufficiency question is about time scheduling of four subjects across four consecutive one hour periods starting at 8:00 a.m. The goal is to determine the time at which Chemistry is taught, based on different pieces of information about the order of subjects. The problem checks whether the learner can map statements to a time line and identify which combinations of statements uniquely fix the slot for Chemistry. Given Data / Assumptions: There are four periods: 8 to 9 a.m., 9 to 10 a.m., 10 to 11 a.m., and 11 a.m. to 12 noon. The subjects are Physics, Chemistry, Mathematics, and Biology, each taught in exactly one period. Statement I says that Mathematics ends at 10:00 a.m. and is immediately preceded by Biology. Statement II says that Physics is taught in the last period. Statement III says that Mathematics is immediately followed by Chemistry. Concept / Approach: We represent each period by its time slot and try to place the subjects based on each statement. If a single statement gives a unique position for Chemistry, it is sufficient. If a statement leaves more than one possible arrangement, it is not sufficient. Next, we test pairs of statements to see whether the ambiguity is removed. Importantly, any combination that uniquely fixes the time of Chemistry is counted as sufficient. Step-by-Step Solution: Step 1: From statement I, Mathematics ends at 10:00 a.m. Therefore Mathematics is in the 9 to 10 a.m. period. Biology is immediately before Mathematics, so Biology is in the 8 to 9 a.m. period. The remaining two subjects, Physics and Chemistry, must then occupy 10 to 11 a.m. and 11 a.m. to 12 noon, but their order is not specified. Step 2: Using only statement I, Chemistry could be at 10 to 11 a.m. or at 11 a.m. to 12 noon. Since there are two possibilities, statement I alone is not sufficient. Step 3: From statement II alone, Physics is in the last period, that is, 11 a.m. to 12 noon. The positions of the other three subjects are not known, so Chemistry could be in any of the three earlier slots. Statement II alone is not sufficient. Step 4: From statement III alone, Mathematics is immediately followed by Chemistry, but there is no information regarding when Mathematics starts or ends. The pair Mathematics followed by Chemistry could occupy the first and second periods, the second and third periods, or the third and fourth periods. Hence statement III alone is also not sufficient. Step 5: Combine statements I and II. From I we know Biology at 8 to 9 a.m. and Mathematics at 9 to 10 a.m. From II we know Physics at 11 a.m. to 12 noon. This leaves only the 10 to 11 a.m. slot for Chemistry, so Chemistry is uniquely fixed at 10 to 11 a.m. Step 6: Combine statements I and III. Statement I fixes Mathematics at 9 to 10 a.m. and Biology at 8 to 9 a.m. Statement III says Mathematics is immediately followed by Chemistry, so Chemistry must be at 10 to 11 a.m. again. The time is now unique. Step 7: Combine statements II and III. From II we know Physics at 11 a.m. to 12 noon. From III we only know that Mathematics and Chemistry are adjacent in the order Mathematics, then Chemistry. However, these two subjects could occupy 8 to 9 and 9 to 10, or 9 to 10 and 10 to 11. Both patterns fit all the information, so Chemistry could be at 9 to 10 a.m. or at 10 to 11 a.m. This pair is not sufficient. Verification / Alternative check: A practical verification is to list all valid permutations under each combination of statements. For I alone, there are two permutations for the remaining subjects. For II alone, there are six permutations for the other three subjects. For III alone, there are three positions where the Mathematics Chemistry pair can be placed. For I with II and for I with III, only one valid overall permutation exists, and in each case Chemistry time is 10 to 11 a.m. For II with III, more than one permutation survives. This confirms the sufficiency pattern found earlier. Why Other Options Are Wrong: Option A claiming only I is sufficient is wrong because Chemistry can be placed in two different periods under statement I. Option B claims that either I or II alone is sufficient, which is incorrect because II alone clearly leaves three choices for Chemistry. Option C gives sufficiency to II alone, which is wrong for the same reason. The only correct description is that I combined with II, or I combined with III, is sufficient, which is option D. Common Pitfalls: Learners sometimes forget that the periods are fixed one hour blocks and misread phrases like immediately before or immediately after. Others may assume that last period must be 10 to 11 a.m., ignoring the fourth period. It is also easy to overlook that statement III does not specify any absolute time, only relative order. Careful mapping of each statement to the time line avoids these mistakes. Final Answer: The correct option is that statements I and II together or statements I and III together are sufficient to answer the question, which corresponds to option D.

Question 16

Total money with Naresh and Ajay is 28 percent of that with Usman. How much money does Ajay have?  Consider the following statements:  I. Usman has a total of Rs 75000. II. The ratio of the money of Naresh to the money of Ajay is 1 : 3.  Using the d…

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Introduction / Context: This question is a classic example of data sufficiency in percentage and ratio based word problems. The total money held by Naresh and Ajay is given as a fixed percentage of Usman amount, and two statements provide additional numerical details. The task is to decide which combination of statements allows us to compute Ajay exact amount, not simply to perform that calculation. Given Data / Assumptions: The combined money of Naresh and Ajay is 28 percent of the total money of Usman. Statement I says that Usman has Rs 75000. Statement II says that the ratio of the amount of Naresh to the amount of Ajay is 1 : 3. All amounts are assumed to be positive real numbers expressed in rupees. Concept / Approach: We translate the information into algebraic equations. Let U, N, and A denote the amounts of Usman, Naresh, and Ajay. The percentage relation gives N + A as a fixed percentage of U. The ratio relation gives N and A in a fixed ratio. We then check which statements give enough equations to determine A uniquely. If a statement alone leaves free variables, it is not sufficient; if both together close the system, they are necessary. Step-by-Step Solution: Step 1: From the initial condition we have N + A = 28 percent of U, so N + A = 0.28 * U. Step 2: From statement I, U = 75000. Substituting into the earlier equation gives N + A = 0.28 * 75000 = 21000. Therefore the sum of the amounts of Naresh and Ajay is 21000, but the individual portions N and A are still unknown. Step 3: Notice that with statement I alone, there are infinitely many pairs (N, A) such that N + A = 21000, so the amount of Ajay cannot be fixed. Statement I alone is not sufficient. Step 4: From statement II, N : A = 1 : 3. That means N = k and A = 3k for some positive constant k. However, without knowing N + A or some other relation connecting their sum to a number, k remains free. Statement II alone is therefore not sufficient. Step 5: Combine statements I and II. From earlier, N + A = 21000 and N : A = 1 : 3. Substitute N = k and A = 3k. We get k + 3k = 21000, so 4k = 21000, and k = 5250. Hence N = 5250 and A = 15750. Now Ajay amount is uniquely determined. Step 6: Since neither statement alone is sufficient, but their combination yields a unique value for Ajay, we classify the sufficiency as requiring both statements together. Verification / Alternative check: A quick alternative check is to count unknowns and equations. Without using any statements, we have three unknowns U, N, and A and one relation N + A = 0.28 * U. Statement I adds a second equation by fixing U, and statement II adds a third equation by fixing the ratio of N to A. With all three relations, the system becomes determined and allows exact computation of N and A. Removing either statement removes one equation and leaves infinitely many solutions, which confirms that both statements are necessary. Why Other Options Are Wrong: Option A is wrong because statement I alone stops at N + A = 21000, without a way to split that sum between Naresh and Ajay. Option B is wrong because statement II alone only fixes the ratio and never gives a total. Option C, suggesting that either statement alone suffices, is clearly incorrect. Option E, which claims that even both statements together are not sufficient, is also wrong because the combination gives a fully determined system and leads to a unique value for Ajay amount. Only option D correctly identifies that both statements together are necessary to get the exact figure. Common Pitfalls: A common mistake is to assume that knowing the percentage relation and Usman amount automatically gives Ajay amount, without noticing that the combined amount includes Naresh as well. Another error is to misread the ratio 1 : 3 as giving absolute numbers instead of proportional values. In data sufficiency questions, it is important to separate information about totals from information about ratios and ensure both are present before concluding that a single share can be computed. Final Answer: The data in both statements I and II together are necessary to answer the question, so the correct option is D.

Question 17

Among four friends, Siddhartha, Nikunj, Vipul, and Mukul, who is the youngest?  Consider the following statements:  I. Vipul is younger than Mukul but older than both Siddhartha and Nikunj. II. Mukul is the oldest among the four friends. III. Siddha…

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Introduction / Context: This data sufficiency question concerns ordering by age. Four friends are compared, and the aim is to identify the youngest among them based on three statements. The challenge is not to find all ages or even the full order, but to decide which statements provide enough information to fix the youngest person uniquely. Given Data / Assumptions: The four friends are Siddhartha, Nikunj, Vipul, and Mukul. Statement I: Vipul is younger than Mukul but older than both Siddhartha and Nikunj. Statement II: Mukul is the oldest among the four friends. Statement III: Siddhartha is older than Nikunj. No two friends share exactly the same age unless implied, and all comparisons are consistent. Concept / Approach: We treat the statements as inequalities on a number line of ages. If one combination of statements fully orders the four friends or at least identifies the lowest position without contradictions, that combination is sufficient. If more than one youngest candidate remains possible under a combination, that combination is not sufficient. The focus is on relative ordering, not on numeric ages. Step-by-Step Solution: Step 1: Translate statement I. It says Mukul is older than Vipul, and Vipul is older than both Siddhartha and Nikunj. In order form, this gives Mukul > Vipul > Siddhartha and Mukul > Vipul > Nikunj. However, we still do not know the relative order between Siddhartha and Nikunj. Step 2: Consider statement I alone. From Mukul > Vipul > Siddhartha and Mukul > Vipul > Nikunj, the youngest could be Siddhartha or Nikunj since the relation between these two is not specified. Therefore statement I alone is not sufficient to identify the youngest. Step 3: Consider statement II alone. Mukul is the oldest, but there is no information about the relative order of the other three friends. Any of Siddhartha, Nikunj, or Vipul could be the youngest. Hence statement II alone is not sufficient. Step 4: Consider statement III alone. Siddhartha is older than Nikunj. This only compares two of the four friends and gives no information about Vipul and Mukul, so statement III alone is not sufficient. Step 5: Combine statements I and II. Statement II says Mukul is the oldest, which is already consistent with statement I because Mukul is older than Vipul there. However, the unresolved comparison between Siddhartha and Nikunj remains, so the youngest could still be either Siddhartha or Nikunj. Thus I and II together are not sufficient. Step 6: Combine statements II and III. Mukul is oldest and Siddhartha is older than Nikunj, but no information connects Vipul to the other three. Vipul could be younger than Nikunj or older than all except Mukul. Hence we cannot decide who is youngest, so II and III together are not sufficient. Step 7: Combine statements I and III. From I we have Mukul > Vipul > Siddhartha and Mukul > Vipul > Nikunj. From III we add Siddhartha > Nikunj. Together these relations yield Mukul > Vipul > Siddhartha > Nikunj. Now the full order is fixed, and Nikunj is clearly the youngest. Verification / Alternative check: To verify, we can draw a simple age line and add inequalities progressively. Under statements I and III together, no flexibility remains for the relative order; any attempt to place Nikunj above someone else violates at least one inequality. Under any other combination, at least two people can swap positions at the bottom without breaking any given relation, which confirms that only I plus III is sufficient to decide the youngest. Why Other Options Are Wrong: Option A claims that statement I alone is sufficient, but that ignores the missing comparison between Siddhartha and Nikunj. Option B suggests I and II together are enough, which is incorrect because II only confirms what I already implies about Mukul being older than Vipul and does not affect the uncertainty at the bottom. Option C, involving II and III, still leaves the position of Vipul undetermined. Only option D, which uses I and III together, removes all ambiguity and pinpoints Nikunj as the youngest. Common Pitfalls: Learners sometimes misread phrases like younger than but older than as giving a complete ranking when they actually leave gaps. Another common mistake is to treat the statement that someone is oldest as automatically determining the youngest, which is not true unless enough other comparisons are provided. Careful construction of the relative order with each new piece of information avoids such errors. Final Answer: The correct choice is that statements I and III together are sufficient to answer the question, so the correct option is D.

Question 18

Gaurav ranks eighteenth from the top in his class. What is his rank from the bottom of the class?  Consider the following statements:  I. There are 47 students in the class. II. Jatin, who is also in the same class, ranks tenth from the top and thir…

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Introduction / Context: This data sufficiency question deals with rankings from the top and from the bottom in a class. We are told Gaurav rank from the top and asked to find his rank from the bottom. Two statements provide information about the total number of students, one directly and one indirectly through another student ranking. The aim is to decide which statements allow us to compute Gaurav rank from the bottom. Given Data / Assumptions: Gaurav ranks eighteenth from the top in his class. Statement I: There are 47 students in the class. Statement II: Jatin ranks tenth from the top and thirty eighth from the bottom. Ranking is strictly by position with no ties, and the class size is fixed. Concept / Approach: The standard relationship between a position from the top, a position from the bottom, and the total number of students is: total = rank from top + rank from bottom minus 1. If we know any two of these three quantities for a student, we can find the third. Once the total number of students is known, Gaurav rank from the bottom follows directly from his rank from the top. Step-by-Step Solution: Step 1: Use statement I alone. If there are 47 students in the class and Gaurav is eighteenth from the top, then his rank from the bottom is 47 minus 18 plus 1. That is 29 plus 1 equals 30. So Gaurav is thirtieth from the bottom. Step 2: This shows that statement I alone is sufficient, because once the total number of students is given, the calculation is straightforward and unique. Step 3: Now use statement II alone. For Jatin, the relationship total = rank from top + rank from bottom minus 1 becomes total = 10 + 38 minus 1. That is total = 47. Thus statement II alone also yields the total number of students as 47, without directly stating it. Step 4: After deducing that there are 47 students from statement II, we can repeat the same calculation as in Step 1 for Gaurav, again finding that Gaurav is thirtieth from the bottom. Step 5: Because each individual statement allows us to determine the class size and therefore Gaurav rank from the bottom, each statement alone is sufficient. Therefore the correct classification is that either I alone or II alone is sufficient. Verification / Alternative check: As a cross check, consider whether any other class size could be consistent with statement II. If the class size were not 47, the sum of Jatin ranks from both ends minus 1 would not equal the total. Since the equality holds, the total must be exactly 47. Consequently, the logic of the calculation for Gaurav is forced. There is no alternative interpretation that changes his position from the bottom, so sufficiency is confirmed. Why Other Options Are Wrong: Option A claims only statement I is sufficient and implicitly suggests that statement II alone is not sufficient, which contradicts the fact that II allows us to compute the class size. Option B incorrectly gives sufficiency only to statement II. Option D claims that both statements together are necessary, which is not correct because we do not need to combine them. Option E, which says that even both are not sufficient, is clearly false because we have already obtained Gaurav rank from the bottom with each individual statement. Common Pitfalls: Learners sometimes forget the minus one in the relationship between top rank, bottom rank, and total students, leading to incorrect totals. Others may treat the information about Jatin as irrelevant because it does not mention Gaurav by name, overlooking that class size is the essential bridge. Remembering the standard formula and focusing on what is needed to link to the target student prevents these mistakes. Final Answer: The data either in statement I alone or in statement II alone are sufficient to answer the question, so the correct option is C.

Question 19

How many pages of book X did Robert read on Sunday?  Consider the following statements:  I. Book X has 300 pages, and two thirds of the pages had been read by Robert before Sunday. II. Robert read the last 40 pages of the book on the morning of Mond…

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Introduction / Context: This data sufficiency problem is based on reading progress through a book. Robert reads a certain part of book X before Sunday, some part on Sunday, and some part again on Monday. The question asks how many pages he read on Sunday, and the statements provide information about the total pages and pages read at specific times. The focus is to judge whether the statements contain enough information to determine the Sunday reading. Given Data / Assumptions: Book X has a total of 300 pages. Statement I: Two thirds of the book were read by Robert before Sunday. Statement II: Robert read the last 40 pages of the book on Monday morning. Pages are read in order, with no skipping and no rereading, and all counts are exact. Concept / Approach: Let the total pages be T, pages read before Sunday be B, pages read on Sunday be S, and pages read on Monday be M. Since Robert eventually finishes the book, B + S + M = T. Data sufficiency requires checking whether the statements fix S uniquely. If S remains undetermined with one statement but determined when both are combined, then both statements together are necessary. Step-by-Step Solution: Step 1: From statement I, two thirds of the book were read before Sunday. For a book of 300 pages, two thirds of 300 is 200 pages. Thus B = 200 pages read before Sunday. Step 2: Using statement I alone, we know that 100 pages remain to be read at the start of Sunday, but we do not know how many of those pages are read on Sunday and how many on Monday. Therefore statement I alone is not sufficient to determine S. Step 3: From statement II, Robert read the last 40 pages on Monday. This tells us M = 40. However, it does not give any information about how many pages were left at the end of Sunday, nor about total pages or the fraction read before Sunday. Hence statement II alone is also not sufficient. Step 4: Now combine statements I and II. We already know from I that B = 200 and T = 300, so there are 100 pages left after Saturday. From II we know M = 40 pages on Monday. Since Robert finishes the book, we must have B + S + M = T, so 200 + S + 40 = 300. Step 5: Solve for S. The equation 200 + S + 40 = 300 simplifies to 240 + S = 300. Therefore S = 300 minus 240 equals 60 pages. Thus Robert read exactly 60 pages on Sunday. Step 6: Because neither statement alone gives enough information but their combination does, both statements together are necessary to answer the question. Verification / Alternative check: As a check, consider how many distributions of Sunday and Monday pages are possible under each statement. Under statement I alone, any pair (S, M) satisfying S + M = 100 with S and M positive would work, so there are many possibilities. Under statement II alone, S could be any number at all, as long as the book ends with 40 pages on Monday. Only when we impose both B = 200 and M = 40, along with T = 300, do we get a single value for S. Therefore the necessity of both statements is confirmed. Why Other Options Are Wrong: Option A is incorrect because statement I alone leaves an entire range of possible values for S. Option B is incorrect because statement II alone does not mention total pages or pages read before Sunday. Option C is wrong because neither statement alone suffices. Option E, which says that even both statements together are not sufficient, contradicts the clear derivation of S = 60 pages. Only option D correctly recognises that both statements together are required and sufficient. Common Pitfalls: Learners may assume that if a certain fraction of the book has been read before Sunday and a specific number of pages is read on Monday, then Sunday reading can be guessed from proportion, without doing the exact calculation. Another mistake is to forget that the sum of all reading sessions must equal the total pages. Careful bookkeeping with variables and the equation B + S + M = T prevents these oversights. Final Answer: The data in both statements I and II together are necessary to answer the question, so the correct option is D.

Question 20

How is Rakesh related to Keshav?  Consider the following statements:  I. Tapan has a wife named Nisha who is the paternal aunt of Keshav. II. Rakesh is the brother of a friend of Nisha.

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Introduction / Context: This data sufficiency question involves family relationships and social connections. The task is to identify the relationship of Rakesh to Keshav using information about Tapan, Nisha, and a friend of Nisha. The key is to understand that social friendships do not necessarily imply blood relationships, and to check whether the statements can force any specific family link between Rakesh and Keshav. Given Data / Assumptions: Statement I: Tapan has a wife named Nisha, and Nisha is the paternal aunt of Keshav. This means Nisha is a sister of Keshav father. Statement II: Rakesh is the brother of a friend of Nisha. Friends of Nisha can be unrelated people from outside the family, unless stated otherwise. No extra information is given about Rakesh parents or siblings beyond what is in statement II. Concept / Approach: We need to determine whether the statements can fix a unique family relationship between Rakesh and Keshav, such as cousin, uncle, or no blood relation. In data sufficiency, if we can construct multiple possible family trees that satisfy the statements but give different answers about Rakesh relationship to Keshav, then the data are not sufficient to answer the question. Step-by-Step Solution: Step 1: Interpret statement I. Since Nisha is the paternal aunt of Keshav, she is a sister of Keshav father. Tapan is the husband of Nisha, so Tapan is the paternal uncle of Keshav by marriage. Step 2: Notice that statement I only describes how Tapan and Nisha are related to Keshav. It does not mention Rakesh at all. Therefore, statement I alone clearly cannot determine Rakesh relationship to Keshav. Step 3: Interpret statement II. Rakesh is the brother of a friend of Nisha. This means there exists some person F who is a friend of Nisha, and Rakesh and F are siblings. Nothing in the statement says that F is related to Nisha by blood or marriage. F could be a colleague, a neighbour, or any unrelated person. Step 4: With statement II alone, we have no link at all to Keshav, since Keshav is not mentioned. Thus statement II alone is also not sufficient. Step 5: Combine statements I and II. The first statement anchors Nisha within Keshav family as a paternal aunt. The second statement introduces Rakesh as the sibling of Nisha friend. However, it still does not say that this friend is a relative. Both F and Rakesh can be completely unrelated to the family of Keshav and may simply have a social connection to Nisha. Step 6: Construct possible scenarios. In one scenario, Nisha friend F is a colleague from work who has no family connection to Keshav. Then Rakesh, as F brother, is also not related to Keshav by blood or marriage. In another scenario, F could be a cousin of Nisha, making some distant connection possible, but even then the exact relation between Rakesh and Keshav varies with the family tree and is not forced by the statements. Step 7: Since more than one consistent arrangement is possible and none is required by the data, no unique relationship can be identified between Rakesh and Keshav. Therefore, even the two statements together are not sufficient. Verification / Alternative check: A fast way to verify is to ask whether any blood or marital link is explicitly defined between Rakesh and the core family of Keshav. Statement I defines such a link for Tapan and Nisha, but statement II defines Rakesh only through friendship, not kinship. Friendship alone cannot be used to infer relations like cousin or uncle. Because the chain from Keshav to Rakesh always passes through an unrestricted friendship, there is no forced family relation. Why Other Options Are Wrong: Options A and B wrongly claim sufficiency for a single statement, which is impossible because each statement mentions only one side of the connection. Option C claims that either statement alone is sufficient, which is plainly incorrect. Option D claims that both statements together are necessary and sufficient, yet even when they are combined, the information does not constrain the friend of Nisha in a way that would fix Rakesh relation. Only option E correctly states that even both statements together do not provide enough data. Common Pitfalls: Learners often assume that any person mentioned near the family must be some kind of relative. This is not valid unless specified. Another common confusion is between social labels like friend and family relations such as cousin or uncle. In data sufficiency questions about relations, it is important not to invent missing family links, and to remember that friends can be completely external to the family tree. Final Answer: The data even in both statements together are not sufficient to answer the question, so the correct option is E.

Data Sufficiency Questions