Question 1

In the list of numbers 253, 136, 352, 324, 631 and 244, which one is the odd man out because it does not share the same digit-sum property as the others?

Accepted Answer

Introduction / Context: This is a classic odd-man-out problem involving three-digit numbers. The idea is that most of the numbers in the list share a hidden property related to their digits, while one number does not. Recognizing this hidden property is essential in many reasoning and aptitude examinations. Given Data / Assumptions: The given numbers are: 253, 136, 352, 324, 631 and 244. We are told that exactly one of these numbers does not belong to the same group as the others. We look only at the digits themselves and simple properties like sums of digits, reversals, and similar relationships. Concept / Approach: When you see three-digit numbers with no obvious arithmetic progression or multiplication pattern, a very common strategy is to examine the sum of their digits. Sometimes all numbers except one have the same digit sum or share a property such as being equal to 10, 12, or another special value. That is the clue here as well. Step-by-Step Solution: Step 1: Compute the sum of digits for each number.253 → 2 + 5 + 3 = 10.136 → 1 + 3 + 6 = 10.352 → 3 + 5 + 2 = 10.631 → 6 + 3 + 1 = 10.244 → 2 + 4 + 4 = 10.324 → 3 + 2 + 4 = 9.Step 2: Observe the pattern. For every number except one, the sum of its digits is equal to 10.Step 3: Only 324 has a digit sum equal to 9, which is different from the common digit sum of 10 shared by all the others. Verification / Alternative check: We can quickly re-check the digit sums to avoid mistakes. All of 253, 136, 352, 631 and 244 give 10 when adding their digits. Only 324 gives a different total. There is no need to look for more complicated patterns, because a very neat and unique property (digit sum equal to 10) already groups five of the numbers together, leaving 324 alone. Why Other Options Are Wrong: 136, 352 and 631 may look different at first glance, but each of them still has a digit sum of 10, so they fit the same pattern as 253 and 244. Choosing any of them as the odd one out would ignore this clear and simple property. Therefore, none of these can be the unique odd number in the set. Common Pitfalls: Students may waste time searching for more complex relationships such as prime factors, squares, or cubic relationships, or may focus on the order of digits rather than their sum. In many odd-man-out questions, the key is a very simple digit property like parity, divisibility or digit sums, so it is important to check those first. Final Answer: The only number whose digits do not sum to 10 is 324, so it is the odd man out.

Question 2

In the number sequence 36, 54, 18, 27, 9, 18.5, 4.5, which single term is incorrect and breaks the alternating multiply-and-divide pattern?

Accepted Answer

Introduction / Context: This series question involves alternating multiplication and division by simple fractions. The goal is to detect that pattern and then identify the single term that does not follow it. Such questions strengthen your understanding of fractional operations and pattern recognition. Given Data / Assumptions: The sequence is: 36, 54, 18, 27, 9, 18.5, 4.5. We assume that the intended pattern uses simple ratios, such as multiplying by 3/2 or dividing by 3, and that exactly one term is incorrect. Concept / Approach: Because the numbers go up and down, an alternating pattern is likely: multiply by a fixed factor, then divide by another fixed factor, and so on. The simplest ratio to test here is 3/2 (which is 1.5) for multiplication and 3 for division, since 36 to 54 suggests multiplication by 3/2, and 54 to 18 suggests division by 3. Step-by-Step Solution: Step 1: Check the first few transitions.36 → 54: 36 * (3/2) = 36 * 1.5 = 54.54 → 18: 54 / 3 = 18.18 → 27: 18 * (3/2) = 27.27 → 9: 27 / 3 = 9.Step 2: Up to this point, the pattern is clear: multiply by 3/2, then divide by 3, and repeat.Step 3: Continue the same pattern: 9 * (3/2) = 9 * 1.5 = 13.5 (not 18.5). Then 13.5 / 3 = 4.5.Step 4: The last term 4.5 is consistent with the pattern if we use 13.5 in place of 18.5. Therefore, 18.5 is the only number that does not fit the intended rule. Verification / Alternative check: Write the ideal pattern explicitly: 36, 54, 18, 27, 9, 13.5, 4.5, where the operations are *3/2, /3, *3/2, /3, *3/2, /3. Every transition satisfies either multiplying by 1.5 or dividing by 3. The given sequence breaks this rule only once, at the position where 18.5 appears instead of 13.5. Hence 18.5 is clearly the wrong term. Why Other Options Are Wrong: 36, 27 and 9 all satisfy the multiply-by-3/2 or divide-by-3 rule when placed in the correct positions. Changing any of them would destroy multiple correct transitions and would not restore a neat alternating pattern, so they cannot be the unique culprit. Common Pitfalls: Some learners may only compare each term with its immediate neighbor, without spotting the alternating nature of the operations. Others may try to fit a single operation (only multiplication or only division) which will not work. Remember to consider repeating cycles such as multiply then divide in series questions. Final Answer: The incorrect term that breaks the multiply-by-3/2, divide-by-3 pattern is 18.5.

Question 3

In the decreasing sequence 52, 51, 48, 43, 34, 27, 16, which one term is wrong because it does not follow the regular subtraction pattern?

Accepted Answer

Introduction / Context: This question presents a decreasing series of numbers and asks you to identify which one does not fit a simple subtraction pattern. Such questions test your ability to detect consistent differences between consecutive terms and to spot a single anomaly in that pattern. Given Data / Assumptions: The sequence is 52, 51, 48, 43, 34, 27, 16. We assume that the intended sequence follows a simple rule involving subtracting odd numbers in a recognizable order. Exactly one term is assumed to be incorrect. Concept / Approach: When a series decreases, it is natural to check the differences between successive terms. Often, those differences themselves follow a simple pattern, such as successive odd numbers: 1, 3, 5, 7, 9, etc. Identifying this pattern allows us to see which term breaks the rule. Step-by-Step Solution: Step 1: Compute consecutive differences.52 → 51: difference = -1.51 → 48: difference = -3.48 → 43: difference = -5.43 → 34: difference = -9.34 → 27: difference = -7.27 → 16: difference = -11.Step 2: Compare these differences with the ideal sequence of consecutive odd numbers: -1, -3, -5, -7, -9, -11.Step 3: Up to 48 → 43, the pattern matches -1, -3, -5. The next odd numbers should be -7, -9, -11 in that order.Step 4: From 43, subtracting 7 should give 36, not 34. Then 36 - 9 = 27 and 27 - 11 = 16 would perfectly match the remaining terms.Step 5: Therefore, the term that should be 36 has been incorrectly written as 34. The incorrect term in the series is 34. Verification / Alternative check: Reconstruct the corrected series using the intended pattern of subtracting consecutive odd numbers: 52 - 1 = 51, 51 - 3 = 48, 48 - 5 = 43, 43 - 7 = 36, 36 - 9 = 27, 27 - 11 = 16. This gives the sequence 52, 51, 48, 43, 36, 27, 16, which is perfectly regular. Only the originally given value 34 breaks this structure. Why Other Options Are Wrong: 52, 51 and 27 all fit correctly into the consistent pattern of subtracting consecutive odd numbers. Changing any of them would disrupt several differences at once and would not restore a clean sequence. The only single change that makes the pattern fully correct is replacing 34 with 36, so 34 must be the wrong term. Common Pitfalls: Students sometimes look only at approximate size changes and miss the exact sequence of odd-number differences. Another frequent error is to miscalculate one or more of the differences, which can hide the underlying pattern. Writing out each difference clearly is essential for accurate reasoning. Final Answer: The term that does not follow the intended subtraction pattern is 34.

Question 4

In the series 7, 8, 18, 57, 228, 1165, 6996, which one number is wrong because it does not follow the clear multiplication-plus pattern followed by the others?

Accepted Answer

Introduction / Context: This question involves a non-trivial number series where each term is generated from the previous one using a combination of multiplication and addition. The task is to detect the consistent rule and identify which term breaks that rule. Such questions are slightly more challenging and often appear in higher-level aptitude and reasoning exams. Given Data / Assumptions: The series is: 7, 8, 18, 57, 228, 1165, 6996. We assume that all terms except one follow a rule of the form “multiply by an integer and then add the same integer,” with the integer increasing step by step. Exactly one term is incorrect. Concept / Approach: A common pattern for such sequences is: next term = current term * n + n, where n increases by 1 at each step (for example, *1 + 1, then *2 + 2, then *3 + 3, and so on). We test whether this rule fits the series and see which term violates it. Step-by-Step Solution: Step 1: Start from 7 and check the transitions.7 to 8: 7 * 1 + 1 = 8 (fits the rule with n = 1).8 to 18: 8 * 2 + 2 = 16 + 2 = 18 (fits with n = 2).18 to 57: 18 * 3 + 3 = 54 + 3 = 57 (fits with n = 3).Step 2: Continue the same pattern.The next step should use n = 4: 57 * 4 + 4 = 228 + 4 = 232. Hence, the correct next term should be 232.Step 3: However, the series gives 228 instead of 232. So the term 228 does not follow the *4 + 4 rule.Step 4: Check the following term using the corrected value 232: With n = 5, we get 232 * 5 + 5 = 1160 + 5 = 1165, which matches the given series.Step 5: Finally, with n = 6, we check 1165 * 6 + 6 = 6990 + 6 = 6996, which again matches the given value. Verification / Alternative check: If we keep 228 as given, the rule *n + n cannot be applied consistently from one term to the next, because 57 * 4 + 4 is not equal to 228. In contrast, replacing 228 with 232 restores a perfect pattern: *1 + 1, *2 + 2, *3 + 3, *4 + 4, *5 + 5, *6 + 6. Both 1165 and 6996 fit this pattern when 232 is used, so 228 must be the incorrect term. Why Other Options Are Wrong: 57, 1165 and 6996 all match the rule when the fourth term is correctly taken as 232. Changing any of these would break the clean *n + n pattern across the sequence. Therefore, they cannot be considered the unique wrong term. Common Pitfalls: Students may try to guess a simpler multiplication-only pattern or may assume inconsistent operations between different pairs of terms. The key is to notice the gradual increase of the multiplier and the same number being added, which is a common construction in exam series questions. Final Answer: The only term that does not follow the “multiply by n and add n” pattern is 228.

Question 5

In the sequence 6, 13, 18, 25, 30, 37, 40, which single term is incorrect because it breaks the alternating +7 and +5 pattern?

Accepted Answer

Introduction / Context: This question presents an increasing number sequence where the increments follow a simple alternating pattern. Your task is to identify which number does not respect that pattern. Such problems are common in reasoning tests and help you practice working with recurring difference patterns. Given Data / Assumptions: The sequence is: 6, 13, 18, 25, 30, 37, 40. We assume there is a regular rule involving additions by fixed numbers (most likely 5 and 7), and exactly one term is wrong. Concept / Approach: When a series increases but not by a constant amount, the first step is to check the differences between consecutive terms. If those differences alternate between two values, we can detect that and see which term breaks the pattern. This is the case here. Step-by-Step Solution: Step 1: Compute the differences between consecutive terms.6 → 13: difference = +7.13 → 18: difference = +5.18 → 25: difference = +7.25 → 30: difference = +5.30 → 37: difference = +7.37 → 40: difference = +3.Step 2: Notice the pattern: the differences should alternate +7, +5, +7, +5, +7, and so on.Step 3: Following this pattern strictly, after 37 we should add +5, not +3. So the correct next term should be 37 + 5 = 42.Step 4: Therefore, 40 is the only term that does not fit the alternating +7, +5 pattern and is the wrong number in the sequence. Verification / Alternative check: Rebuild the sequence using the ideal alternating differences: starting from 6, we get 6 + 7 = 13, 13 + 5 = 18, 18 + 7 = 25, 25 + 5 = 30, 30 + 7 = 37, and 37 + 5 = 42. This yields the correct pattern 6, 13, 18, 25, 30, 37, 42. The given sequence differs only in the last term, which is 40 instead of 42. Why Other Options Are Wrong: 25, 30 and 37 all fit perfectly into the alternating +7 and +5 structure. Changing any of them would break multiple differences at once and would not restore a clean pattern. Only replacing 40 by 42 keeps the simple alternation intact, so 40 must be the erroneous value. Common Pitfalls: Test-takers sometimes look for a single constant difference or try to impose multiplication rules where there are none. Another mistake is to ignore the last step because the change seems small. Even small deviations are important in series questions, so always compute every difference carefully. Final Answer: The term that breaks the alternating +7 and +5 pattern is 40.

Question 6

Among the alphanumeric codes 2T0, 1R8, 2Y4 and 1P6, which one does not belong to the group based on the relationship between the digits and the letter's position in the alphabet?

Accepted Answer

Introduction / Context: This question uses alphanumeric codes where each code consists of a digit, a letter, and another digit. The task is to identify the odd man out, that is, the code that does not follow the same rule as the others. Such problems test both number sense and familiarity with alphabetical positions. Given Data / Assumptions: The codes given are: 2T0, 1R8, 2Y4 and 1P6. We assume that each letter corresponds to its position in the English alphabet: A = 1, B = 2, C = 3, ..., Z = 26. We also assume there is a logical relationship between the two digits and the letter in each code. Concept / Approach: A natural pattern to test is whether the letter's position equals the two-digit number formed by putting the first and last digits together. In other words, for 2T0 we check whether T is the 20th letter; for 1R8 we check whether R is the 18th letter, and so on. If three codes satisfy this property and one does not, that one will be the odd man out. Step-by-Step Solution: Step 1: Evaluate 2T0. Combine the digits 2 and 0 to get 20. The letter T is indeed the 20th letter of the alphabet, so 2T0 follows the pattern.Step 2: Evaluate 1R8. Combine the digits 1 and 8 to get 18. The letter R is the 18th letter, so 1R8 also follows the same rule.Step 3: Evaluate 1P6. Combine the digits 1 and 6 to get 16. The letter P is the 16th letter, so 1P6 again fits the pattern.Step 4: Evaluate 2Y4. Combine the digits 2 and 4 to get 24. The letter Y is the 25th letter of the alphabet, not the 24th. Thus, 2Y4 does not satisfy the rule. Verification / Alternative check: We can quickly list the positions of the letters: R is 18, P is 16, T is 20 and Y is 25. The numeric parts of the codes are 20, 18, 24 and 16, from 2T0, 1R8, 2Y4 and 1P6 respectively. Only in the case of 2Y4 is the numeric value (24) not equal to the alphabetical position (25). Therefore, 2Y4 is clearly the only code that breaks the pattern. Why Other Options Are Wrong: 2T0, 1R8 and 1P6 each perfectly obey the rule “letter position = two-digit number formed by the outer digits.” Choosing any of these as the odd man out would ignore this neat and consistent property, so they cannot be considered correct answers. Common Pitfalls: Some candidates may focus on the sum or difference of the digits, or look for divisibility properties, and miss the simple relation to alphabet positions. Another mistake is to miscount letter positions (for example, confusing R with the 17th letter instead of the 18th). Carefully counting from A = 1 to the target letter avoids this error. Final Answer: The only code that does not satisfy the digit-to-letter position rule is 2Y4.

Question 7

In the number series 16, 33, 65, 131, 261, ( ? ), which value should replace the missing term to maintain the pattern?

Accepted Answer

Introduction / Context: This question asks you to insert the missing number in a series where each term appears to be roughly double the previous one, with a small correction. This is a typical number-series puzzle that evaluates your ability to analyze how each term is generated from its predecessor. Given Data / Assumptions: The given series is: 16, 33, 65, 131, 261, ( ? ). You must decide which of the options 523, 521, 613 or 721 fits the pattern. We assume that a simple arithmetic relationship of the form “multiply by 2 and then add or subtract 1” is used repeatedly. Concept / Approach: When numbers nearly double at each step but do not match exact powers of 2, it is natural to test the rule: next term = 2 * current term ± 1. Here, we will check whether an alternating +1, -1 pattern is followed when doubling each term. Step-by-Step Solution: Step 1: Move from 16 to 33. Compute 2 * 16 = 32, then 32 + 1 = 33.Step 2: Move from 33 to 65. Compute 2 * 33 = 66, then 66 - 1 = 65.Step 3: Move from 65 to 131. Compute 2 * 65 = 130, then 130 + 1 = 131.Step 4: Move from 131 to 261. Compute 2 * 131 = 262, then 262 - 1 = 261.Step 5: The pattern is now clear: starting from 16, each term is twice the previous one, alternately adding 1, then subtracting 1. The signs are +1, -1, +1, -1, and so on.Step 6: To get the next term from 261, we double it and then add 1 (because the last operation was -1, so the next must be +1): 2 * 261 = 522, and 522 + 1 = 523. Verification / Alternative check: We can reconstruct the entire pattern explicitly: 16 * 2 + 1 = 33, 33 * 2 - 1 = 65, 65 * 2 + 1 = 131, 131 * 2 - 1 = 261, 261 * 2 + 1 = 523. No other option fits this simple and consistent rule. Values like 521 or 613 would break the neat alternation of +1 and -1 after doubling. Why Other Options Are Wrong: 521 differs from 523 by 2 and cannot be obtained from 261 using a simple double-and-add-or-subtract-1 pattern. Similarly, 613 and 721 are far away from 2 * 261, so they would require arbitrary operations that do not match the earlier steps of the series. Therefore, none of them can be correct. Common Pitfalls: Many candidates notice the approximate doubling but ignore the small corrections. Others may try to fit a more complex polynomial pattern instead of testing the straightforward rule “2n ± 1.” Recognizing small consistent adjustments is crucial for solving such problems quickly. Final Answer: The missing number that keeps the pattern intact is 523.

Question 8

Among the following, which is the odd one out: Sapphire, Ruby, Topaz or Granite?

Accepted Answer

Introduction / Context: This is a general knowledge and classification question. You are asked to choose the odd one out among four given names: Sapphire, Ruby, Topaz and Granite. Problems like this test your awareness of everyday terms, materials and categories, rather than numerical reasoning. Given Data / Assumptions: The options are four common names associated with stones or minerals: Sapphire, Ruby, Topaz and Granite. We assume you know that some of these are precious or semi-precious gemstones, while others are ordinary rocks used in construction and industry. Concept / Approach: The key idea is to classify each item into its correct category based on basic general knowledge. Three of the items belong to the same category (gemstones used in jewellery), while one belongs to a different category (an igneous rock used mainly as a building material). The item from the different category is the odd one out. Step-by-Step Solution: Step 1: Consider Sapphire.Sapphire is a precious gemstone, typically blue, composed mainly of the mineral corundum. It is widely used in jewellery.Step 2: Consider Ruby.Ruby is also a precious gemstone made of corundum, distinguished by its deep red color. It is a classic gemstone in rings and necklaces.Step 3: Consider Topaz.Topaz is a silicate mineral, valued as a semi-precious gemstone. It comes in various colors and is also commonly used in jewellery.Step 4: Consider Granite.Granite is a coarse-grained igneous rock composed mainly of quartz, feldspar and mica. It is used for countertops, flooring, paving and as a construction material. It is not classified as a gemstone.Step 5: Therefore, three items (Sapphire, Ruby, Topaz) are gemstones, and one (Granite) is an ordinary rock primarily used in construction. Verification / Alternative check: You can cross-check by thinking about where you usually see each of these. Sapphire, Ruby and Topaz are seen in rings, pendants and other jewellery pieces, and are sold in jewellery shops. Granite, however, is seen in kitchen slabs, tiles, monuments and building facades. This everyday knowledge confirms that Granite belongs to a different category from the other three. Why Other Options Are Wrong: Sapphire, Ruby and Topaz all share the property of being gemstones used as ornaments. Removing any of them as the odd one out would leave two gemstones grouped with a construction rock, which does not make sense from a classification point of view. Therefore, they cannot be correct answers. Common Pitfalls: Sometimes candidates may be unsure whether Topaz qualifies as a gemstone or may focus on color or price differences rather than basic classification. The safest and most objective way is to check whether each name refers to a gemstone or to a common rock. Once that is done, the answer becomes clear and unambiguous. Final Answer: The odd one out, because it is a rock used mainly in construction and not a gemstone, is Granite.

Question 9

In the sequence 10, 25, 45, 54, 60, 75, 85, which number is the odd one out based on divisibility by 5?

Accepted Answer

Introduction / Context: This odd-man-out question uses a very simple divisibility property. You are given a list of numbers and asked to identify which one does not share the same divisibility feature as the others. Such questions help you quickly recall and apply basic divisibility rules, which are extremely useful in mental arithmetic and aptitude tests. Given Data / Assumptions: The numbers given are 10, 25, 45, 54, 60 and 85. We assume that the intended property is a standard one taught in school, such as divisibility by 5, 10 or some other small integer. Our task is to find which number fails to meet that common property. Concept / Approach: A very common and easy-to-spot rule is divisibility by 5. A number is divisible by 5 if and only if its last digit is 0 or 5. Looking at the list, almost all numbers end with 0 or 5, which strongly suggests that divisibility by 5 is the relevant property here. The number that does not share this property will be the odd one out. Step-by-Step Solution: Step 1: Examine the last digit of each number.10 ends with 0 → divisible by 5.25 ends with 5 → divisible by 5.45 ends with 5 → divisible by 5.54 ends with 4 → not divisible by 5.60 ends with 0 → divisible by 5.85 ends with 5 → divisible by 5.Step 2: Observe that every number except 54 ends in 0 or 5 and is divisible by 5.Step 3: 54, ending with 4, does not satisfy the divisibility rule for 5 and so is the odd one out. Verification / Alternative check: We can quickly confirm by performing the division 54 / 5, which gives 10.8, not an integer. For all other numbers, division by 5 yields an integer result: 10 / 5 = 2, 25 / 5 = 5, 45 / 5 = 9, 60 / 5 = 12, and 85 / 5 = 17. Therefore, 54 alone is not divisible by 5, which confirms it as the outlier. Why Other Options Are Wrong: 10, 45 and 85, as well as 25 and 60, clearly share the property of being multiples of 5. Removing any of them as the odd one out would leave a set where the remaining numbers still share the divisibility-by-5 property and 54 still does not, which would be inconsistent. So they cannot be the correct answer. Common Pitfalls: Some candidates may overthink the question and look for more complex relationships involving prime factors or sequences, overlooking the very simple and obvious rule. In many exam questions, the simplest shared property is the intended one, especially when last digits are clearly suggestive as in this case. Final Answer: The only number that is not divisible by 5 is 54, so it is the odd one out.

Question 10

In the series of numbers 125, 127, 130, 135, 142, 153, 165, which term is the odd one out because it breaks the pattern of increasing differences based on prime numbers?

Accepted Answer

Introduction / Context: This problem presents a number sequence whose terms increase according to a pattern involving prime numbers. The task is to identify which term does not conform to this pattern. Such questions are designed to assess your ability to link series differences with known special numbers, such as primes. Given Data / Assumptions: The sequence is: 125, 127, 130, 135, 142, 153, 165. We assume that the link between consecutive terms is based on adding successive prime numbers (for example 2, 3, 5, 7, 11, 13, and so on). One term is incorrect. Concept / Approach: The first step is to compute the differences between consecutive terms and check whether those differences follow a familiar pattern. Because the increments are small and seem to grow irregularly, it is natural to test whether they match the early prime numbers in order: 2, 3, 5, 7, 11, 13, etc. Step-by-Step Solution: Step 1: Compute the differences between consecutive terms.127 - 125 = 2.130 - 127 = 3.135 - 130 = 5.142 - 135 = 7.153 - 142 = 11.165 - 153 = 12.Step 2: Now observe the differences: 2, 3, 5, 7, 11 are all prime numbers in increasing order.Step 3: Following this pattern, after adding 11, the next logical difference should be the next prime, which is 13, not 12.Step 4: If we add 13 to 153, we get 153 + 13 = 166. So the term after 153 should be 166 to maintain the prime-difference pattern.Step 5: The given value is 165 instead of 166. Therefore, 165 is the unique term that does not fit the established pattern. Verification / Alternative check: Rewriting the sequence using the intended pattern, we have: 125 + 2 = 127, 127 + 3 = 130, 130 + 5 = 135, 135 + 7 = 142, 142 + 11 = 153, and 153 + 13 = 166. In this corrected series, all increments match consecutive primes. The only discrepancy between the given and the corrected series is at the last term, confirming that 165 is the odd one out. Why Other Options Are Wrong: 127, 142 and 153 all help maintain the prime differences 2, 3, 5, 7 and 11. If you remove any of these terms, you destroy the consistent sequence of prime increments. Only changing the last term allows the full pattern with consecutive primes to remain intact. Common Pitfalls: Some students may suspect a more complex polynomial relationship, or may think of squares or cubes. Others may not recognize the list of differences as prime numbers and thus miss the key observation. Always check whether differences correspond to familiar special sequences such as primes, odd numbers or square numbers. Final Answer: The only term that breaks the pattern of adding consecutive primes is 165.

Question 11

In the series 5, 16, 6, 16, 7, 16, 9, which one number is wrong because it breaks the pattern of alternating 16 with consecutive integers?

Accepted Answer

Introduction / Context: This series question is built on a very straightforward alternating pattern. The number 16 appears repeatedly in every second position, while the other positions contain consecutive integers. You are asked to find out which term does not follow this simple rule. Given Data / Assumptions: The sequence is: 5, 16, 6, 16, 7, 16, 9. We assume that 16 is intended to appear at every alternate position, and that the non-16 terms should form a sequence of consecutive integers. One term is incorrect. Concept / Approach: When one number is repeated at fixed intervals in a series, it is sensible to separate the series into two subseries: one for the repeated value and one for the changing values. Here, 16 repeats regularly in the 2nd, 4th and 6th positions, so we focus on the 1st, 3rd, 5th and 7th terms to check whether they form a simple pattern like consecutive numbers. Step-by-Step Solution: Step 1: Write the sequence with positions: (1) 5, (2) 16, (3) 6, (4) 16, (5) 7, (6) 16, (7) 9.Step 2: Observe the terms in even positions: 16, 16, 16. These are all equal, so they are consistent.Step 3: Now examine the odd-position terms: 5 (position 1), 6 (position 3), 7 (position 5), 9 (position 7).Step 4: We can see that 5, 6 and 7 are consecutive integers. The natural continuation would be 8 as the next consecutive number, not 9.Step 5: Therefore, the last term in the sequence should be 8 to continue the consecutive integer pattern, and the given value 9 is incorrect. Verification / Alternative check: If we reconstruct the ideal series, it would be: 5, 16, 6, 16, 7, 16, 8. This has the repeated value 16 at every alternate position and the non-16 terms 5, 6, 7, 8 forming a simple consecutive integer sequence. In the given series, only the last odd-position term (9) breaks this rule, confirming that it is the wrong number. Why Other Options Are Wrong: 6 and 7 both keep the consecutive pattern alive and are placed correctly between the 16s. The value 16 itself is consistently placed in positions 2, 4 and 6, so it also fits the pattern. Only 9 fails to continue the sequence 5, 6, 7, 8 and therefore stands out as the error. Common Pitfalls: Some test-takers may focus on the differences between adjacent terms rather than noticing the alternating structure. They may try to apply a single rule to the entire series, which looks irregular. Recognizing the two interleaved subseries is the key insight for solving this type of question quickly. Final Answer: The term that breaks the alternating 16 and consecutive integer pattern is 9.

Question 12

In the sequence 3125, 256, ?, 4, 1, which number should replace the question mark to continue the pattern of descending powers?

Accepted Answer

Introduction / Context: This question involves recognizing numbers as powers of integers. You are given a series 3125, 256, ?, 4, 1 and asked to find the missing term. Such problems test your knowledge of exponents and your ability to see patterns in powers of small integers. Given Data / Assumptions: The series is 3125, 256, ?, 4, 1. We assume each term can be expressed as n^n for some integer n (for example, 5^5, 4^4, 3^3, 2^2, 1^1), or at least as powers of decreasing integers. Our goal is to identify the appropriate missing value that fits this descending pattern. Concept / Approach: Notice that 3125 is a well-known power: 3125 = 5^5. Similarly, 256 is 4^4, and 4 is 2^2, while 1 is 1^1. This strongly suggests that the sequence is composed of consecutive terms of the form n^n, with n decreasing from 5 down to 1. Therefore, the missing term should be 3^3, which equals 27. Step-by-Step Solution: Step 1: Express each known term as a power.3125 = 5^5.256 = 4^4.4 = 2^2.1 = 1^1.Step 2: Observe the pattern. The base and the exponent are the same, and the base decreases by 1 each time: 5, 4, 3, 2, 1.Step 3: The missing term should correspond to 3^3.Step 4: Compute 3^3 = 3 * 3 * 3 = 27.Step 5: So, the full series becomes 3125 (5^5), 256 (4^4), 27 (3^3), 4 (2^2), 1 (1^1). Verification / Alternative check: The sequence 5^5, 4^4, 3^3, 2^2, 1^1 is a standard pattern used in many reasoning questions. Substituting 27 for the missing term gives a monotonic decrease in both the base and the exponent. None of the other options, such as 128, 32 or 64, fits this neat n^n pattern when placed between 256 and 4. Why Other Options Are Wrong: 128 can be written as 2^7 or 4^3, and 32 as 2^5, while 64 is 2^6 or 4^3. None of these forms match the required structure where the base and exponent are equal and decrease step by step from 5 to 1. Therefore, they do not produce the simple and elegant pattern that is clearly intended by the question. Common Pitfalls: Some students may only think of squares and cubes and may not recall that 3125 is 5^5 or that 256 is 4^4. Others may choose numbers based on approximate size rather than recognizing the exponent pattern. When large powers appear, it is useful to remember a few standard values like 3^3 = 27, 4^4 = 256 and 5^5 = 3125. Final Answer: The missing number that continues the descending n^n pattern is 27.

Question 13

In the series 2.5, 3.5, 9, 40, ?, which number should come next to follow the underlying multiplication-and-addition pattern?

Accepted Answer

Introduction / Context: This number series problem involves non-integer terms and a pattern built from multiplication by powers of 2 followed by a small addition. Recognizing that both the multiplier and the added value change systematically is the key to identifying the next term in the series. Given Data / Assumptions: The series is: 2.5, 3.5, 9, 40, ?. You must choose the correct next term from the options 316, 328, 323 and 340. We assume the series uses a consistent rule where each term is obtained by multiplying the previous term by a certain integer and then adding that same integer. Concept / Approach: A good approach is to check ratios and differences. The jump from 2.5 to 3.5 is small, but from 3.5 to 9 and then to 40 it is much larger, suggesting multiplication by increasing integers. We test whether the pattern “multiply by a power of 2 and then add that same power of 2” holds: multiply by 1 and add 1, then multiply by 2 and add 2, then multiply by 4 and add 4, and so on. Step-by-Step Solution: Step 1: From 2.5 to 3.5. We can write this as 2.5 * 1 + 1 = 2.5 + 1 = 3.5.Step 2: From 3.5 to 9. Check 3.5 * 2 + 2 = 7 + 2 = 9. This matches, with multiplier 2 and addition 2.Step 3: From 9 to 40. Check 9 * 4 + 4 = 36 + 4 = 40. This matches, with multiplier 4 and addition 4.Step 4: Observe the pattern in the multipliers and addends: 1, 2, 4. These are powers of 2 (2^0, 2^1, 2^2). The next power of 2 is 8 (2^3).Step 5: Therefore, the next term should be 40 * 8 + 8 = 320 + 8 = 328. Verification / Alternative check: We can summarize the rule as: next term = current term * k + k, where k takes values 1, 2, 4, 8, ... This pattern is regular and uses simple powers of 2. Substituting k = 8 for the step after 40 gives 328. None of the other options maintain this “multiply by k and add k with k doubling each time” structure. Why Other Options Are Wrong: 316, 323 and 340 do not equal 40 * 8 + 8. They would require inconsistent multipliers and addends that do not follow the earlier pattern of 1, 2, 4. Choosing any of them would break the clean power-of-2 based rule, so they cannot be correct. Common Pitfalls: Candidates may only look for additive patterns (such as adding 1, then 5, then 31) and miss the multiplicative structure. Others may not recognize that the multipliers 1, 2 and 4 form a doubling sequence. Checking both multiplication and addition together is very helpful when jumps between terms grow quickly. Final Answer: The number that correctly continues the pattern is 328.

Question 14

In the decreasing sequence 194, 194, 191, 183, 168, ?, which number should come next to follow the pattern in the successive differences?

Accepted Answer

Introduction / Context: This question gives a sequence of numbers that decreases in a non-linear way and asks you to find the next term. The pattern is hidden in the sequence of differences between consecutive terms, which themselves follow a simple rule. Such questions test your ability to recognize patterns several levels deep. Given Data / Assumptions: The sequence is: 194, 194, 191, 183, 168, ?. You must decide which of the options 154, 156, 144 or 143 should replace the question mark. We assume the sequence is generated by subtracting increasingly larger numbers, with a pattern visible in those subtractions. Concept / Approach: When a sequence is not simple arithmetic or geometric, the most effective approach is to calculate first differences and then second differences. Often, the first differences follow a simple progression (such as quadratic or based on odd numbers), and that progression allows us to predict the next term. Step-by-Step Solution: Step 1: Compute the first differences.194 → 194: difference = 0.194 → 191: difference = -3.191 → 183: difference = -8.183 → 168: difference = -15.Step 2: List these differences: 0, -3, -8, -15.Step 3: Compute the second differences (differences of the differences).-3 - 0 = -3.-8 - (-3) = -5.-15 - (-8) = -7.Step 4: We now see the second differences are -3, -5, -7, which is a sequence of consecutive negative odd numbers. The next second difference should be -9.Step 5: To get the next first difference, subtract 9 from the last first difference: -15 - 9 = -24.Step 6: Apply this to find the next term: 168 + (-24) = 168 - 24 = 144. Verification / Alternative check: We can reconstruct the pattern of first differences: 0, -3, -8, -15, -24. The differences between these are -3, -5, -7, -9, which is a clear and consistent pattern of decreasing by consecutive odd numbers. None of the options other than 144 leads to this neat sequence of second differences, so 144 must be the correct choice. Why Other Options Are Wrong: If we choose 154, 156 or 143, the resulting first difference from 168 would not be -24 and would break the second-difference pattern based on consecutive odd numbers. For example, 154 would give a difference of -14, which does not fit naturally after -15 if we expect larger negative jumps. Therefore, these alternatives are inconsistent with the discovered rule. Common Pitfalls: Some students stop after observing the first differences and fail to notice a clear pattern, then resort to guessing. It is important to remember that sometimes patterns appear only in second or even third differences, so computing them systematically is a valuable technique for number series questions. Final Answer: The next term in the sequence, preserving the pattern in consecutive differences, is 144.

Question 15

In the sequence 152, 124, 96, 69, 40, which number is the odd man out based on divisibility by 4?

Accepted Answer

Introduction / Context: This odd-man-out question relies on a basic divisibility rule. You are asked to decide which number among 152, 124, 96, 69 and 40 does not share a simple divisibility property with the others. Such questions help reinforce quick mental checks about multiples of small integers like 2 and 4. Given Data / Assumptions: The given numbers are 152, 124, 96, 69 and 40. We assume that the relevant property involves divisibility by 4, which can be checked using the standard rule: a number is divisible by 4 if and only if its last two digits form a number that is divisible by 4. Concept / Approach: The most efficient strategy is to apply the divisibility-by-4 rule to each number. If four of them are divisible by 4 and one is not, the one that fails this test will be the odd man out. This avoids complex calculations and uses only the last two digits of each number. Step-by-Step Solution: Step 1: Check 152. The last two digits are 52. Since 52 / 4 = 13, 152 is divisible by 4.Step 2: Check 124. The last two digits are 24. Since 24 / 4 = 6, 124 is divisible by 4.Step 3: Check 96. The last two digits are 96. Since 96 / 4 = 24, 96 is divisible by 4.Step 4: Check 40. The last two digits are 40. Since 40 / 4 = 10, 40 is divisible by 4.Step 5: Check 69. The last two digits are 69. Since 69 / 4 is not an integer (it equals 17.25), 69 is not divisible by 4.Step 6: Therefore, 69 alone fails the divisibility-by-4 test and is the odd man out. Verification / Alternative check: We can also look at the even or odd nature of the numbers: 152, 124, 96 and 40 are all even, while 69 is odd. No odd number can be divisible by 4, so this immediately marks 69 as different. The more refined test using the last two digits confirms that all the other four numbers are exact multiples of 4, reinforcing our conclusion. Why Other Options Are Wrong: 124, 96 and 40, as well as 152, are all divisible by 4 and therefore share a common property. Removing any of them as the odd one out would leave a group containing an odd number (69) that is not divisible by 4 together with numbers that are, which would make less sense from a classification viewpoint. Common Pitfalls: Some test-takers may focus only on whether numbers are even or odd and may not notice that all even numbers except 69 also share the richer property of being divisible by 4. While parity is a helpful first check, using the full divisibility rule allows you to justify your choice more strongly and confidently. Final Answer: The only number that is not divisible by 4 is 69, so it is the odd man out.

Question 16

In the following sequence of numbers 1, 4, 9, 16, 22 and 36, which number is the odd one out that does not follow the same pattern?

Accepted Answer

Introduction / Context: This aptitude question tests your ability to recognize number patterns, specifically perfect squares, and identify the term that breaks the pattern. Odd man out questions like this are common in competitive exams because they quickly reveal how comfortable you are with basic number properties and mental observation skills. Given Data / Assumptions: The given sequence is: 1, 4, 9, 16, 22, 36. We assume that there is exactly one term in the list that does not follow the main rule that governs the other terms. All numbers are positive integers. Concept / Approach: The natural approach is to check whether the numbers follow a well known pattern such as squares, cubes, arithmetic progression, or geometric progression. On quick inspection, several of these numbers look like perfect squares of integers. Therefore, the central idea here is to check which numbers are perfect squares and see if one of them does not fit this pattern. Step-by-Step Solution: Check 1: 1 = 1 * 1, so 1 is a perfect square (1^2).Check 2: 4 = 2 * 2, so 4 is a perfect square (2^2).Check 3: 9 = 3 * 3, so 9 is a perfect square (3^2).Check 4: 16 = 4 * 4, so 16 is a perfect square (4^2).Check 5: 36 = 6 * 6, so 36 is a perfect square (6^2).Check 6: 22 cannot be written as n * n for any integer n, so it is not a perfect square. Verification / Alternative check: Another way to verify is to list nearby perfect squares around 22. We know that 4^2 = 16 and 5^2 = 25. Since 22 lies strictly between 16 and 25 and is not equal to either of them, it cannot be a perfect square. All other numbers in the list exactly match the square of an integer, so our conclusion is consistent from multiple viewpoints. Why Other Options Are Wrong: 1 is 1^2 and hence a perfect square, so it follows the pattern and cannot be the odd one out. 4 is 2^2, a perfect square, so it belongs to the pattern. 9 is 3^2, also a perfect square, so it fits the pattern. 16 and 36 are 4^2 and 6^2 respectively, both perfect squares and therefore consistent with the rule of the series. Common Pitfalls: Students sometimes focus only on the increasing differences between terms (for example, 3, 5, 7, 6, 14) and try to find a pattern there, which becomes messy and misleading. The key is to step back and notice familiar shapes like 1, 4, 9, 16, and 36 as squares of 1, 2, 3, 4, and 6. Missing such standard number patterns is a frequent error in time pressured exams. Final Answer: The only number that is not a perfect square in the list is 22, so 22 is the odd man out.

Question 17

In the number series 5, 24, 94, 279, ?, find the next term that correctly continues the pattern.

Accepted Answer

Introduction / Context: This is a higher level number series question where the pattern is not immediately obvious from simple first differences or simple multiplication. Such questions test your ability to look beyond direct differences and to consider second level patterns such as differences of differences. Being comfortable with these ideas is very useful for tough aptitude tests and competitive exams. Given Data / Assumptions: The series is: 5, 24, 94, 279, ? We assume there is a consistent numeric pattern that generates each term from the previous terms. Exactly one correct next term must be chosen from the given alternatives. Concept / Approach: First we look at the differences between consecutive terms, and then at the differences between those differences. When first differences are irregular, series often follow a pattern in their second differences. If the second differences follow an arithmetic pattern, we can extend that pattern to find the next first difference and in turn the next term of the series. Step-by-Step Solution: Step 1: Compute first differences: 24 - 5 = 19, 94 - 24 = 70, 279 - 94 = 185.Step 2: Compute second differences between these: 70 - 19 = 51, 185 - 70 = 115.Step 3: Notice that these second differences themselves increase. The increase from 51 to 115 is 64.Step 4: Continue this logical pattern by adding another 64 to 115, giving the next second difference as 115 + 64 = 179.Step 5: Find the next first difference: previous first difference 185 plus new second difference 179 gives 185 + 179 = 364.Step 6: Add this first difference to the last known term: 279 + 364 = 643, which must be the next term in the series. Verification / Alternative check: We can verify by writing down the pattern of second differences explicitly as 51, 115, and then 179, showing that each time the increment applied is 64. This is consistent and produces a unique next term. None of the other options will maintain this smooth pattern in second differences, which confirms that 643 is the only value that fits the intended structure. Why Other Options Are Wrong: Values like 587, 554, 499, and 489 do not give a consistent sequence of second differences when inserted as the next term. In each of those cases, the second level differences either jump randomly or do not maintain a regular increment of 64. Hence they break the discovered pattern and cannot be correct. Common Pitfalls: Many students stop after checking only first differences or try to guess a direct multiplication pattern. Because the multipliers and additions look irregular at first glance, guesses often fail. The safer method is to compute second differences systematically. Not recognizing that some series are built on second level patterns is a frequent issue in tough number series questions. Final Answer: The correct next term in the series is 643.

Question 18

Among the numbers 343, 2197, 1331 and 121, which one does not belong to the group of perfect cubes?

Accepted Answer

Introduction / Context: This odd man out question checks your familiarity with perfect cubes and basic factorization. In many aptitude tests, such problems help separate candidates who quickly recognize standard number forms from those who rely only on trial and error. The goal is to identify which number does not share the same key property as the rest. Given Data / Assumptions: The four main options are 343, 2197, 1331 and 121. We assume that three of these are perfect cubes of integers while one is not. We need to find the number which breaks this perfect cube pattern. Concept / Approach: A perfect cube is any integer that can be written in the form n^3 where n is an integer. The direct approach is to factor each number or recall common cubes such as 7^3, 11^3 and 13^3. By matching each value to one of these known cubes, we can see which one does not fit the pattern. Step-by-Step Solution: Check 343: 7 * 7 * 7 = 343, so 343 = 7^3 and is a perfect cube.Check 2197: 13 * 13 * 13 = 2197, so 2197 = 13^3 and is a perfect cube.Check 1331: 11 * 11 * 11 = 1331, so 1331 = 11^3 and is a perfect cube.Check 121: 11 * 11 = 121, so 121 = 11^2 which is a perfect square, not a perfect cube. Verification / Alternative check: We can also verify by checking approximate cube roots. The cube root of 343 is 7 which is an integer. The cube root of 2197 is 13 which is an integer. The cube root of 1331 is 11 which is also an integer. However, the cube root of 121 is between 4 and 5 and is not an integer. Therefore, 121 fails the perfect cube test while the others pass it. Why Other Options Are Wrong: 343 is a perfect cube (7^3) and fits the group property. 2197 is a perfect cube (13^3) and also fits the group property. 1331 is a perfect cube (11^3) and belongs to the same family. Therefore none of these can be the odd one out, leaving only 121 as the correct choice. Common Pitfalls: Some learners see that 121 is a very familiar number and immediately think of it as 11^2 and may incorrectly assume all others are squares, which is not correct. Others forget the common cubes beyond 10^3 and struggle with 2197 and 1331. It is helpful to memorize cubes of integers at least up to 15 for exam purposes, as these appear frequently in number system questions. Final Answer: The number that is not a perfect cube is 121.

Question 19

In the series 6, 15, 35, 77, 165, 221, which number is the odd one out that does not follow the underlying pattern?

Accepted Answer

Introduction / Context: This question asks you to identify the wrong or odd term in a sequence. Such number series are designed so that all but one term follow a consistent rule. Your task is to spot that rule and see which number breaks it. Here the series involves multiplication and the use of prime numbers, which are important themes in aptitude and number system problems. Given Data / Assumptions: Sequence given: 6, 15, 35, 77, 165, 221. Exactly one term violates the rule followed by the others. All terms are positive integers. Concept / Approach: Whenever you see numbers like 6, 15, 35 and 77, it is natural to think in terms of products of prime numbers. The usual technique is to factor each term into primes and look for a common structure. In this sequence, we will see that most terms are products of two consecutive primes, which immediately suggests a pattern. Step-by-Step Solution: Factor 6: 6 = 2 * 3, a product of consecutive primes 2 and 3.Factor 15: 15 = 3 * 5, a product of consecutive primes 3 and 5.Factor 35: 35 = 5 * 7, a product of consecutive primes 5 and 7.Factor 77: 77 = 7 * 11, a product of primes 7 and 11 (still consecutive primes).Factor 165: 165 = 3 * 5 * 11 or 15 * 11, not a simple product of two consecutive primes, but it fits as 11 multiplied by the previous prime product 15.Factor 221: 221 = 13 * 17, which are not consecutive primes and do not align with the way earlier terms are constructed. Verification / Alternative check: You can focus only on the pattern that each term is closely connected to prime pairs. Up to 165, every number can be seen as built from consecutive primes or a natural extension of that pattern. However, 221 breaks this logic because 13 and 17 are separated by the prime 15 is not a prime and 221 does not fit a simple consecutive prime product pattern. No reasonable adjustment of the rule keeps 221 consistent with all others. Why Other Options Are Wrong: 6, 15, 35 and 77 each clearly show consecutive prime factor pairs like (2, 3), (3, 5), (5, 7) and (7, 11). 165 can be interpreted as 15 * 11, still connecting back to prime products used earlier in the sequence. Only 221 fails to match this consistent style of construction and so it is the odd one out. Common Pitfalls: Some students only look at differences between terms (9, 20, 42, 88, 56) which appear irregular and confusing. That line of attack does not reveal the structure. The better approach in many series questions is to check for multiplicative patterns and prime factorization. Missing the prime factor pattern can easily lead to incorrect guesses. Final Answer: The term that does not follow the prime factor pattern is 221.

Question 20

In the sequence 56, 72, 90, 110, 132, 150, which term is incorrect or the wrong number in the series?

Accepted Answer

Introduction / Context: This problem is a classic wrong number in series question. You are asked to find which term does not fit a simple numeric pattern. These are very common in bank exams and other competitive tests because they can be solved quickly if you are comfortable with sequences built by adding regular increments. Given Data / Assumptions: Given sequence: 56, 72, 90, 110, 132, 150. Exactly one number is assumed to be wrong. The correct underlying pattern is expected to be simple and consistent. Concept / Approach: When dealing with such sequences, we first calculate the differences between consecutive terms. If the differences themselves follow a simple pattern such as consecutive even numbers, arithmetic progression, or geometric progression, the term that does not maintain this pattern is the wrong one. Here, the focus is on even number increments. Step-by-Step Solution: Compute the differences: 72 - 56 = 16.Next difference: 90 - 72 = 18.Next difference: 110 - 90 = 20.Next difference: 132 - 110 = 22.Next difference: 150 - 132 = 18.From the first four differences we see the clear pattern: 16, 18, 20, 22. These are consecutive even numbers increasing by 2.If the pattern continued correctly, the next difference after 22 should be 24, not 18. So the last term should have been 132 + 24 = 156, not 150. Verification / Alternative check: We can rewrite the correct pattern as: 56, 72, 90, 110, 132, 156, where each term is obtained by adding successive even numbers 16, 18, 20, 22 and 24. This produces a smooth, logical progression. The original series deviates only at the last term. Therefore, 150 is clearly the incorrect number in the sequence. Why Other Options Are Wrong: 56 is the starting term and fits perfectly. 72, 90, 110 and 132 all maintain the pattern of adding consecutive even numbers and are consistent with one another. Only 150 fails to follow the expected increment of 24 from 132 and so it is the only wrong term. Common Pitfalls: Sometimes examinees look for multiplicative relationships instead of additive ones and get stuck. Others may not check all differences carefully and assume a random term is wrong. Always list the differences fully and observe whether they form a pattern such as consecutive even numbers. That quick check avoids unnecessary confusion. Final Answer: The wrong term in the sequence is 150.

Odd Man Out and Series Questions