Question 1

Consider the series 15, 19, 27, 38, 55 and 75. Which number is the odd man out because it has a special power property that the others do not share?

Accepted Answer

Introduction / Context: This problem gives a short list of numbers and asks you to find the odd man out. There is no obvious progression in the differences or ratios, so instead of looking for a series rule between consecutive terms, we should examine individual number properties such as being a perfect square, a perfect cube or having some special factorisation. Given Data / Assumptions: The numbers in the series are: 15 19 27 38 55 75 We assume that one of these numbers has a distinct mathematical property related to powers, while the others are simply composite or prime numbers without that special power structure. Concept / Approach: A good way to approach such questions is to test for perfect powers like squares and cubes. A perfect cube is a number of the form n^3 for some integer n. If only one number in the list is a perfect cube and all others are not, that number can be considered the odd man out based on this structural property. Step-by-Step Solution: Step 1: Check 15. Its prime factorisation is 3 * 5, so it is not a perfect square or cube.Step 2: Check 19. It is a prime number and cannot be expressed as n^2 or n^3 for an integer n greater than 1.Step 3: Check 27. We have 27 = 3 * 3 * 3 = 3^3, which is a perfect cube.Step 4: Check 38. It factors as 2 * 19 and has no exponent higher than 1, so it is not a perfect square or cube.Step 5: Check 55. It factors as 5 * 11, again with no repeated prime factor that would give a higher power.Step 6: Check 75. The factorisation is 3 * 5 * 5, so although it has a squared factor 5^2, the whole number is not a perfect square or cube because the exponent of 3 is only 1. Verification / Alternative check: We can summarise these observations: 27 is the only number that can be written exactly as n^3, with n = 3. All other numbers either have mixed prime factors with exponents 1 or have partial square factors but do not form a perfect square or cube. No other term in the list is a pure power like 2^3, 4^3 or 5^3, which confirms that 27 is structurally unique. Why Other Options Are Wrong: The numbers 38, 55 and 75 are ordinary composite numbers without being complete squares or cubes. They do not have that strong and unique power property. Removing any of them would still leave 27 as a perfect cube among the remaining terms, so they cannot be regarded as the odd ones out under this criterion. Common Pitfalls: Students sometimes focus only on differences between consecutive numbers, which can be messy in this case. When no clear pattern appears in differences or ratios, it is often better to examine properties of individual numbers such as primality, perfect squares or perfect cubes. That method quickly highlights 27 as the only perfect cube in the list. Final Answer: The odd man out, because it is the only perfect cube, is 27.

Question 2

In the number series 0.25, 8, 128, 1024, ?, find the next term by identifying the pattern in the powers of 2 used to generate the sequence.

Accepted Answer

Introduction / Context: This question presents a number series that grows very rapidly: 0.25, 8, 128, 1024, ?. The presence of powers of 2 is a strong hint, since 8, 128 and 1024 are all very familiar powers of 2. The challenge is to uncover how the exponents change from term to term and then use that pattern to find the missing value. Given Data / Assumptions: The known terms of the series are: 0.25 8 128 1024 ? We assume that each term can be written as a power of 2, and that the exponents form a simple pattern that we can extend to find the next exponent and hence the next term. Concept / Approach: First express each term as 2 raised to a power. Then examine the sequence of exponents. If the differences between these exponents follow a recognisable pattern, such as a decreasing arithmetic progression, we can predict the next exponent and compute the corresponding power of 2. Step-by-Step Solution: Step 1: Rewrite each term as a power of 2.0.25 = 1/4 = 2^(-2).8 = 2^3.128 = 2^7.1024 = 2^10.Step 2: List the exponents: −2, 3, 7, 10.Step 3: Find the differences between exponents.From −2 to 3 the difference is +5.From 3 to 7 the difference is +4.From 7 to 10 the difference is +3.Step 4: The differences themselves follow a simple sequence: 5, 4, 3, which decreases by 1 each time. The next difference should therefore be +2.Step 5: Add this next difference to the last exponent: 10 + 2 = 12.Step 6: The next term must therefore be 2^12 = 4096. Verification / Alternative check: We can summarise the rule as: start with exponent −2, then successively add 5, 4, 3 and 2 to get the next exponents. This gives the sequence of exponents −2, 3, 7, 10, 12, which correspond to the numbers 0.25, 8, 128, 1024 and 4096. This reconstruction is fully consistent and leaves no ambiguity about the next term. Why Other Options Are Wrong: The other options 2526, 8486 and 2620 are not powers of 2 and do not fit naturally into the pattern of changing exponents. If we tried to replace 4096 with any of them, the neat stepwise pattern in the powers of 2 would break completely, so they cannot represent the correct continuation of the series. Common Pitfalls: Some learners may try to reason directly from the raw numbers and look at ratios like 8 / 0.25 or 128 / 8, which are not constant. The key is to notice that all visible terms except the first are familiar powers of 2. Once you convert 0.25 to 2^(-2), the exponent pattern becomes much clearer and the problem becomes straightforward. Final Answer: The next number in the series, following the pattern in the powers of 2, is 4096.

Question 3

In the series 7, 11, 19, 35, ?, find the next number by examining the pattern in the successive differences between terms.

Accepted Answer

Introduction / Context: This is a classic number series question where we must determine the next term. The numbers 7, 11, 19 and 35 increase at an accelerating pace, which suggests that the differences between consecutive terms themselves follow a pattern. Spotting this pattern is the key to finding the missing value. Given Data / Assumptions: The series given is: 7 11 19 35 ? We assume that a consistent rule governs the difference between one term and the next, and that this rule can be extended to compute the unknown term. Concept / Approach: When numbers increase at a non constant rate, it is helpful to compute the first differences between consecutive terms. If these differences form a simple pattern such as doubling, increasing by a fixed amount or following a small arithmetic progression, we can use that pattern to obtain the next difference and hence the next term. Step-by-Step Solution: Step 1: Compute the first differences.From 7 to 11 the difference is 11 − 7 = 4.From 11 to 19 the difference is 19 − 11 = 8.From 19 to 35 the difference is 35 − 19 = 16.Step 2: Observe that the differences are 4, 8 and 16, which clearly double each time.Step 3: Following this pattern, the next difference should be 16 * 2 = 32.Step 4: Therefore, the next term in the series is 35 + 32 = 67. Verification / Alternative check: We can restate the series in terms of the rule: start from 7 and repeatedly add differences that double each step. So we have 7, then 7 + 4 = 11, then 11 + 8 = 19, then 19 + 16 = 35, and finally 35 + 32 = 67. This process gives a clean, consistent sequence with no contradictions, confirming that 67 is the unique logical continuation. Why Other Options Are Wrong: Values 131, 94 and 83 do not equal 35 + 32, so they do not respect the doubling difference pattern. If we used any of them, the differences between terms would no longer form the simple sequence 4, 8, 16, 32. Hence those values are not compatible with the observed rule governing the series. Common Pitfalls: Some students may attempt to find a direct multiplication rule from term to term, which does not work well here because the ratio varies. Focusing on first differences is a much more effective strategy whenever you see a steadily increasing but non constant gap between numbers in a series. Final Answer: The next number in the given series is 67.

Question 4

In the series 5, 19, 49, 101, 181, 295, ?, find the missing number by analysing the pattern in the changing differences between consecutive terms.

Accepted Answer

Introduction / Context: This question gives a series of numbers that grow rapidly: 5, 19, 49, 101, 181, 295, ?. The increments between terms are not constant, and they themselves appear to increase in a structured way. This type of problem usually involves examining both the first and second differences to reveal a smooth underlying pattern. Given Data / Assumptions: The known terms in the series are: 5 19 49 101 181 295 ? We assume that a consistent rule dictates the growth of the first differences, which can be captured by looking at the second differences between the terms. Concept / Approach: The general strategy is: First, compute the differences between consecutive terms (first differences). Then, compute the differences between these differences (second differences). If the second differences follow a simple pattern, we can extend that pattern to obtain the next first difference and therefore the next term. Step-by-Step Solution: Step 1: Compute first differences.19 − 5 = 14.49 − 19 = 30.101 − 49 = 52.181 − 101 = 80.295 − 181 = 114.So the first differences are 14, 30, 52, 80 and 114.Step 2: Compute second differences between these first differences.30 − 14 = 16.52 − 30 = 22.80 − 52 = 28.114 − 80 = 34.Step 3: Observe that the second differences are 16, 22, 28, 34, which increase by 6 each time.Step 4: Following this pattern, the next second difference should be 34 + 6 = 40.Step 5: The next first difference should therefore be 114 + 40 = 154.Step 6: Add this to the last known term: 295 + 154 = 449. Verification / Alternative check: We can rebuild the entire series using these rules. Starting from 5, add first differences 14, 30, 52, 80, 114 and 154, where each first difference grows by second differences 16, 22, 28, 34 and 40. This exactly reproduces the known terms and leads logically to 449 as the next term. The pattern is smooth and consistent, with second differences forming a simple arithmetic progression. Why Other Options Are Wrong: Values 401, 351 and 501 do not satisfy the established pattern of second differences increasing by 6. If we plugged any of them into the series, the computed next first differences and second differences would break the smooth 16, 22, 28, 34, 40 structure. Therefore these values are inconsistent with the revealed rule. Common Pitfalls: Many learners stop after calculating first differences and feel that they are irregular. For more advanced series, it is essential to examine second differences as well. Recognising that the second differences themselves form a simple arithmetic progression is the key insight for harder series questions like this one. Final Answer: The missing number that continues the pattern correctly is 449.

Question 5

In the number series 514, 470, ?, 415, 404, find the missing term by identifying the regular pattern in the decreasing differences.

Accepted Answer

Introduction / Context: This problem presents a descending number series with one missing term: 514, 470, ?, 415, 404. The numbers are fairly close together, which suggests that the differences between consecutive terms follow a neat, stepwise pattern. Our job is to uncover this pattern and use it to find the unknown term. Given Data / Assumptions: The series, including the unknown, is: 514 470 ? 415 404 We assume that there is a consistent rule for the amount subtracted at each step, likely involving simple multiples of a small integer. Concept / Approach: A natural strategy is to look at the differences between known consecutive terms and see whether these differences follow a pattern such as a decreasing arithmetic sequence. If we can express each step as subtracting a multiple of some base number, the missing term can be found by continuing that pattern. Step-by-Step Solution: Step 1: Compute the difference from the first term to the second term.514 − 470 = 44.Step 2: Compute the difference from the fourth term to the fifth term.415 − 404 = 11.Step 3: Observe that 44 and 11 look like 4 * 11 and 1 * 11 respectively. This hints at subtracting multiples of 11 with coefficients 4, 3, 2 and 1 in order.Step 4: Following this idea, the sequence of subtractions could be: −44, −33, −22, −11.Step 5: Apply this pattern step by step.From 514 subtract 44 to get 514 − 44 = 470.From 470 subtract 33 to get 470 − 33 = 437.From 437 subtract 22 to get 437 − 22 = 415.From 415 subtract 11 to get 415 − 11 = 404. Verification / Alternative check: This reconstruction gives the complete series 514, 470, 437, 415, 404 with a clear rule: each term is obtained by subtracting multiples of 11 that decrease by 11 each time (44, 33, 22, 11). Every step fits perfectly, which confirms that the missing term must be 437 in order to preserve this regular pattern. Why Other Options Are Wrong: Values 441, 426 and 420 do not fit into the coherent subtraction pattern of −44, −33, −22, −11. If any of them were used in place of 437, the required differences to reach 415 and 404 would be irregular and would not be simple multiples of 11 in decreasing order. Hence they are inconsistent with the logic of the series. Common Pitfalls: Students may try to guess the missing number by rough estimation instead of systematically checking the differences. For series with regular step decreases, always test whether the differences can be expressed as multiples of a common number. That approach quickly reveals the underlying rule and leads to a precise answer. Final Answer: The missing number in the series is 437.

Question 6

In the sequence 3, 4, 14, 48, 576, 27648, which one number is the odd one out based on the rule that, from the third term onward, each term equals the product of the previous two?

Accepted Answer

Introduction / Context: This question asks you to find the odd one out in the sequence 3, 4, 14, 48, 576, 27648. At first glance the numbers grow very quickly and the ratios between consecutive terms are not constant. Instead of looking for a simple geometric progression, we should test whether later terms can be generated as products of earlier ones. Given Data / Assumptions: The sequence is: 3 4 14 48 576 27648 We assume that there may be a rule connecting each term with the two immediately preceding terms, and that one of the given numbers breaks this rule. Concept / Approach: A powerful pattern to check is whether a term equals the product of the previous two terms. If we can find a consistent rule of the form a(n+1) = a(n) * a(n−1) for all but one term, that exceptional term is naturally identified as the odd one out. We will reconstruct a corrected sequence to see which number does not fit. Step-by-Step Solution: Step 1: Assume the first two terms are 3 and 4.Step 2: If each new term were the product of the previous two, then the third term should be 3 * 4 = 12.Step 3: Using this idea, generate further terms:Fourth term would be 4 * 12 = 48.Fifth term would be 12 * 48 = 576.Sixth term would be 48 * 576 = 27648.Step 4: This gives a consistent product based sequence: 3, 4, 12, 48, 576, 27648.Step 5: Compare this intended sequence with the given one: the only discrepancy is that the given third term is 14 instead of 12. Verification / Alternative check: Once we see that 3, 4, 12, 48, 576, 27648 follows the rule a(n+1) = a(n) * a(n−1), it is clear that 14 does not satisfy this rule because 3 * 4 = 12 and not 14. All other terms fit perfectly as products of their two predecessors. This confirms that 14 is the only term that breaks an otherwise very clean and elegant pattern. Why Other Options Are Wrong: The numbers 4, 48 and 27648 are essential components of the product pattern. Removing any of them would destroy the chain of products and make it impossible to maintain a consistent rule based on a(n+1) = a(n) * a(n−1). Only the value 14 can be changed to 12 without disturbing the rest of the sequence. Common Pitfalls: Students may first try to find a constant ratio or simple additive pattern, which does not work here. When ratios vary but terms grow dramatically, it is a good idea to test whether each term can be constructed from the previous two, often via multiplication. This perspective quickly exposes 14 as the misfit. Final Answer: The odd one out, which does not fit the product of previous two terms rule, is 14.

Question 7

In the sequence 6, 3, 3, 4.5, 10, which one number is the odd one out if the intended pattern is to repeatedly halve the first term and then multiply by 1, then by 1.5, and so on?

Accepted Answer

Introduction / Context: This question presents a short sequence of numbers: 6, 3, 3, 4.5, 10. You are asked to identify the odd one out. The sequence involves both whole numbers and decimals, so it is natural to consider operations such as halving and multiplying by fractional factors. The aim is to find a smooth pattern that all but one term follow. Given Data / Assumptions: The sequence is: 6 3 3 4.5 10 We assume that the first four numbers follow a simple and consistent pattern, and that the last number may have been misgenerated relative to that pattern. Concept / Approach: Start by examining how each term might be obtained from the previous one. The initial terms suggest a halving followed by a multiplication, for example 6 to 3 can be seen as halving, and 3 to 3 as multiplication by 1. Continuing this idea with a gradually increasing multiplier leads to a clear expectation for the fifth term. The term that fails this expectation will be the odd one out. Step-by-Step Solution: Step 1: From 6 to 3: 6 / 2 = 3, so the second term is half of the first.Step 2: From 3 to 3: 3 * 1 = 3, so the third term is the second term multiplied by 1.Step 3: From 3 to 4.5: 3 * 1.5 = 4.5, so the fourth term is the third term multiplied by 1.5.Step 4: Following this pattern, the next multiplier should reasonably be 2 (an increase of 0.5 again), giving 4.5 * 2 = 9.Step 5: However, the given fifth term is 10, not 9, which suggests that 10 does not fit the smooth pattern of halving and then multiplying by 1, 1.5, 2, and so on. Verification / Alternative check: We can summarise the intended pattern as: start at 6, then half it to get 3, then multiply by 1 to stay at 3, then multiply by 1.5 to get 4.5, and finally multiply by 2 to get 9. This yields the consistent sequence 6, 3, 3, 4.5, 9. Comparing this with the given sequence 6, 3, 3, 4.5, 10 shows that only the last term deviates from the expected continuation. Why Other Options Are Wrong: The values 6, 3 and 4.5 all follow naturally from the rule described above. Removing any of them would break the halving and then gradually increasing multiplier pattern. Only 10 fails to fit into this structure, since the correct term should have been 9 according to the identified rule. Common Pitfalls: Students sometimes attempt to force a single arithmetic or geometric progression on all terms, which can be misleading when the sequence is built from stepwise changes in the operation. Recognising that the sequence uses both division and multiplication by incremental factors makes the logic much clearer. Final Answer: The number that does not fit the established pattern is 10.

Question 8

In the number series 5, 4, 9, 32, 273, which number is the odd man out based on the property of being a prime versus a composite number?

Accepted Answer

Introduction / Context: This question tests basic number theory ideas about prime and composite numbers. You are given a small set of numbers and asked to identify the odd man out. The quickest way to proceed is to classify each number as prime or composite and then see which one has a different classification from the rest. Given Data / Assumptions: The series of numbers is: 5 4 9 32 273 We assume that all numbers are positive integers and that the distinction between prime and composite numbers is the key idea being tested. Concept / Approach: A prime number is a natural number greater than 1 that has exactly two distinct positive divisors, namely 1 and the number itself. A composite number has more than two positive divisors. To find the odd man out, we simply determine which of the numbers is prime and which are composite. If one number alone is prime and all others are composite, that prime will be the odd one out. Step-by-Step Solution: Step 1: Examine 5. Its only positive divisors are 1 and 5, so 5 is a prime number.Step 2: Examine 4. The divisors of 4 are 1, 2 and 4, so it has more than two divisors and is composite.Step 3: Examine 9. The divisors are 1, 3 and 9, again more than two, so 9 is composite.Step 4: Examine 32. The divisors include 1, 2, 4, 8, 16 and 32, so it is clearly composite.Step 5: Examine 273. It factors as 3 * 7 * 13, so it has many divisors and is also composite. Verification / Alternative check: To confirm, note that 5 is the only number in the list that cannot be broken down into a product of smaller natural numbers other than 1 and itself. Every other term has at least one non trivial factorisation, such as 4 = 2 * 2, 9 = 3 * 3, 32 = 2^5 and 273 = 3 * 7 * 13. This clearly separates 5 from the rest. Why Other Options Are Wrong: The numbers 4, 9, 32 and 273 are all composite and share the common feature of having more than two factors. Selecting any of them as the odd one out would leave the prime number 5 grouped together with composite numbers, which would not match the natural mathematical grouping of the set. Common Pitfalls: Some learners may attempt to spot more complicated patterns like powers or special factor relationships. While such patterns sometimes exist, in this question the simplest and cleanest distinction is between prime and composite numbers. Recognising prime numbers quickly is a useful exam skill. Final Answer: The only prime number in the series, and therefore the odd man out, is 5.

Question 9

In the number series 410, 409, 413, 404, ?, find the next term by identifying the pattern of adding and subtracting consecutive square numbers.

Accepted Answer

Introduction / Context: This series alternates up and down: 410, 409, 413, 404, ?. The changes between terms are not constant, but they suggest a link with small square numbers. Many aptitude series questions use a pattern where you add and subtract consecutive squares or other familiar values. Given Data / Assumptions: The known terms are: 410 409 413 404 ? We assume that each step involves adding or subtracting a square number such as 1^2, 2^2, 3^2, 4^2, with signs alternating between minus and plus. Concept / Approach: The strategy is to compute the differences between consecutive terms and check whether these differences match small perfect squares with alternating signs. Once that structure is confirmed, we can continue the pattern by using the next square number with the appropriate sign and hence find the missing term. Step-by-Step Solution: Step 1: Compute the difference from 410 to 409: 409 − 410 = −1, which is −1^2.Step 2: Compute the difference from 409 to 413: 413 − 409 = +4, which is +2^2.Step 3: Compute the difference from 413 to 404: 404 − 413 = −9, which is −3^2.Step 4: The pattern so far is: subtract 1^2, add 2^2, subtract 3^2. The next logical step is to add 4^2.Step 5: Compute 4^2 = 16.Step 6: Add this to the last known term: 404 + 16 = 420. Verification / Alternative check: We can rewrite the series according to this rule: start with 410, then subtract 1 to get 409, then add 4 to get 413, then subtract 9 to get 404, then add 16 to reach 420. This sequence uses consecutive squares 1, 4, 9 and 16, with signs alternating minus, plus, minus, plus. The pattern is perfectly consistent and leaves no room for another value in place of 420. Why Other Options Are Wrong: Values 412, 415 and 418 would require adding 8, 11 or 14 to 404 instead of 16. These differences are not perfect squares and do not fit into the neat sequence of 1^2, 2^2, 3^2, 4^2 with alternating signs. Therefore, choosing any of them would break the discovered rule. Common Pitfalls: Some students may try to find a constant difference or ratio across the series, which is not present here. Instead, recognising that small square numbers often feature in exam series is very useful. Checking whether observed differences are squares is a quick and effective technique. Final Answer: The next number in the series, obtained by adding 4^2 to 404, is 420.

Question 10

In the list of numbers 56, 64, 48, 90, 16 and 144, which one is the odd one out based on divisibility by 8?

Accepted Answer

Introduction / Context: This odd one out problem is built around a simple divisibility property. The numbers 56, 64, 48, 90, 16 and 144 are all reasonably small, so it is natural to test their divisibility by a fixed integer. Spotting which numbers are or are not divisible by a chosen value quickly reveals the misfit. Given Data / Assumptions: The numbers provided are: 56 64 48 90 16 144 We assume that five of these numbers are divisible by 8, while one is not, and this divisibility property is the intended basis for identifying the odd one out. Concept / Approach: To check divisibility by 8, we can divide each number by 8 and see whether the result is an integer. If the quotient is whole with no remainder, then the number is divisible by 8. The unique number that fails this test will be the odd one out. Step-by-Step Solution: Step 1: Check 56. Compute 56 / 8 = 7, which is an integer, so 56 is divisible by 8.Step 2: Check 64. Compute 64 / 8 = 8, which is an integer, so 64 is divisible by 8.Step 3: Check 48. Compute 48 / 8 = 6, which is an integer, so 48 is divisible by 8.Step 4: Check 16. Compute 16 / 8 = 2, which is an integer, so 16 is divisible by 8.Step 5: Check 144. Compute 144 / 8 = 18, which is an integer, so 144 is divisible by 8.Step 6: Check 90. Compute 90 / 8 = 11.25, which is not an integer, so 90 is not divisible by 8. Verification / Alternative check: We can also reason through factorisations. For example, 56 = 7 * 8, 64 = 8 * 8, 48 = 6 * 8, 16 = 2 * 8 and 144 = 18 * 8. Each of these has 8 as a factor. However, 90 factors as 2 * 3 * 3 * 5 and has no factor 8, which again shows that 90 is different from the others with respect to divisibility by 8. Why Other Options Are Wrong: The numbers 56, 64, 48 and 16 are all clean multiples of 8, as is 144. Removing any one of them as the odd one out would still leave a group dominated by multiples of 8 while 90 remains a non multiple. Thus they cannot be considered the correct odd term. Common Pitfalls: Students sometimes search for complex patterns involving squares, cubes or prime factors, when a simple divisibility test would suffice. Whenever several numbers in a set are clearly multiples of a small integer, it is worth checking whether this property characterises the entire group except for one number. Final Answer: The only number in the list that is not divisible by 8 is 90.

Question 11

In the number series 6, 6, 9, 18, 45, ?, find the next term by analysing the pattern in the changing multiplication factors between terms.

Accepted Answer

Introduction / Context: This problem gives a series 6, 6, 9, 18, 45, ? and asks you to find the next number. The terms increase, but the growth is not purely arithmetic or geometric. Instead, the multipliers between consecutive terms themselves follow a simple pattern, which is the key to solving the question. Given Data / Assumptions: The known terms are: 6 6 9 18 45 ? We assume that each term (from the second onward) is obtained by multiplying the previous term by a factor that gradually increases in a regular way. Concept / Approach: To reveal the pattern, we calculate the ratio of each term to the previous term. If these ratios form a simple sequence, such as starting at 1 and increasing by 0.5 each time, we can extend that sequence to find the next ratio and thus the next term in the series. Step-by-Step Solution: Step 1: Find the ratio from the first term to the second: 6 / 6 = 1. So the second term is 6 * 1.Step 2: Find the ratio from the second term to the third: 9 / 6 = 1.5.Step 3: Find the ratio from the third term to the fourth: 18 / 9 = 2.Step 4: Find the ratio from the fourth term to the fifth: 45 / 18 = 2.5.Step 5: The ratios are 1, 1.5, 2 and 2.5. These increase by 0.5 each time.Step 6: Following this pattern, the next ratio should be 2.5 + 0.5 = 3.Step 7: Multiply the last known term by this ratio to get the next term: 45 * 3 = 135. Verification / Alternative check: We can restate the rule as follows: Start at 6, then multiply by 1 to get 6, by 1.5 to get 9, by 2 to get 18, by 2.5 to get 45 and by 3 to get 135. The pattern in the multipliers is extremely regular: 1, 1.5, 2, 2.5, 3, which confirms that the series is built in a systematic way and that 135 is the only value that fits this structure. Why Other Options Are Wrong: Values 87, 99.75 and 115.5 do not equal 45 multiplied by 3 and do not fit any simple extension of the ratio pattern. If any of them were used, the multipliers between terms would no longer increase by a consistent 0.5 step, breaking the logical progression of the sequence. Common Pitfalls: Some learners focus exclusively on differences between consecutive terms instead of looking at ratios. In series where the magnitudes of terms grow in a way that suggests repeated multiplying rather than adding, checking the ratios is a superior strategy that often reveals a clear pattern. Final Answer: The next term in the series, obtained by multiplying 45 by 3, is 135.

Question 12

In the number sequence 123, 112, 133, 112, 143, which number is the odd man out if, in the correct pattern, the sum of the first two digits should equal the third digit?

Accepted Answer

Introduction / Context: This question involves three digit numbers arranged in a small sequence: 123, 112, 133, 112, 143. You are asked to pick the odd man out. The key idea is to look at the relationship between the individual digits of each number rather than treating the numbers as ordinary values in an arithmetic series. Given Data / Assumptions: The numbers are: 123 112 133 112 143 We assume that a consistent rule links the first two digits to the third digit in four of these numbers, while one number breaks this internal digit sum rule. Concept / Approach: A natural pattern to test is whether the third digit equals the sum of the first two digits. For example, in 123, we can ask whether 1 + 2 equals 3. If this rule holds for most of the numbers in the list and fails for exactly one number, that exception will be the odd one out. Step-by-Step Solution: Step 1: Examine 123. The first two digits are 1 and 2. Their sum is 1 + 2 = 3, which matches the third digit.Step 2: Examine 112. The first two digits are 1 and 1. Their sum is 1 + 1 = 2, which matches the third digit.Step 3: Examine 133. The first two digits are 1 and 3. Their sum is 1 + 3 = 4, which matches the third digit.Step 4: Examine the repeated 112 again. As before, 1 + 1 = 2, which matches the third digit.Step 5: Examine 143. The first two digits are 1 and 4. Their sum is 1 + 4 = 5, but the third digit is 3, not 5. So 143 does not satisfy the sum rule. Verification / Alternative check: We can now see that four numbers, namely 123, 112, 133 and the second 112, follow the pattern: third digit equals the sum of the first two digits. The fifth number, 143, fails this test because the sum of its first two digits is 5, while the last digit is 3. There is no second consistent rule that would include 143 with the others, so it clearly stands out as different. Why Other Options Are Wrong: Numbers like 112 and 133 are completely consistent with the sum pattern. Removing any of them as the odd one would leave a set where 143 remains the only number not obeying the digit sum rule. Hence they cannot be considered the correct odd one out. Common Pitfalls: Some learners may look for patterns based on the overall numeric values or differences between numbers instead of examining digit relationships. In many reasoning questions involving multi digit numbers, the real pattern lies inside the digits rather than in the full number values. Always check for digit sums, products or positions when you see such sequences. Final Answer: The number that breaks the sum of first two digits equals third digit pattern is 143.

Question 13

In the list of numbers 12, 48, 168, 502 and 1260, which one is the odd man out based on divisibility by 3?

Accepted Answer

Introduction / Context: This odd man out problem focuses on the basic concept of divisibility by 3. The numbers 12, 48, 168, 502 and 1260 vary in size, but one of them differs from the others with respect to divisibility. Recognising this simple property allows us to quickly identify the outlier. Given Data / Assumptions: The numbers under consideration are: 12 48 168 502 1260 We assume that all but one of these numbers are divisible by 3, and that divisibility by 3 is the central property being tested. Concept / Approach: The divisibility rule for 3 states that a number is divisible by 3 if and only if the sum of its digits is a multiple of 3. To solve the problem, we simply apply this rule to each number in turn. The number that fails the test is the odd one out. Step-by-Step Solution: Step 1: Check 12. The sum of its digits is 1 + 2 = 3, which is divisible by 3, so 12 is a multiple of 3.Step 2: Check 48. The sum of its digits is 4 + 8 = 12, which is divisible by 3, so 48 is a multiple of 3.Step 3: Check 168. The sum of its digits is 1 + 6 + 8 = 15, which is divisible by 3, so 168 is a multiple of 3.Step 4: Check 1260. The sum of its digits is 1 + 2 + 6 + 0 = 9, which is divisible by 3, so 1260 is a multiple of 3.Step 5: Check 502. The sum of its digits is 5 + 0 + 2 = 7, which is not divisible by 3, so 502 is not a multiple of 3. Verification / Alternative check: We can also verify by direct division. 12 / 3 = 4, 48 / 3 = 16, 168 / 3 = 56 and 1260 / 3 = 420, all of which are integers. In contrast, 502 / 3 gives a non integer result. These calculations confirm that 502 is the only number in the list that fails to be divisible by 3. Why Other Options Are Wrong: Numbers 48, 168 and 1260 all pass the divisibility by 3 test, just like 12. They therefore share a common property and belong to the same group. Removing any of them as the odd man out would leave 502, which still has a fundamentally different divisibility property compared with the rest. Common Pitfalls: Sometimes students overcomplicate such questions by looking for sophisticated series patterns or factor structures. It is important to first test very basic properties like divisibility by 2, 3, 5, 9 or 11. In this example, a simple application of the digit sum rule immediately reveals the correct answer. Final Answer: The only number that is not divisible by 3 is 502.

Question 14

In the decimal number series 24.3, 23.1, 20.7, 17.1, 12.4, which value is the odd one out if the intended differences should be simple multiples of 1.2?

Accepted Answer

Introduction / Context: This question features a decreasing decimal series: 24.3, 23.1, 20.7, 17.1, 12.4. You are asked to find the odd one out. The differences between these decimals suggest a pattern based on a fixed step size, namely 1.2, and the term that breaks this regular difference pattern is the outlier. Given Data / Assumptions: The series is: 24.3 23.1 20.7 17.1 12.4 We assume that the intended structure is a sequence where each new term is formed by subtracting successive multiples of 1.2 from the previous term. Concept / Approach: We calculate the differences between consecutive terms and see whether they are multiples of 1.2. If the first three differences follow a clear pattern like −1.2, −2.4, −3.6 and the last step does not continue this rule, the final term is likely incorrect or out of place. Step-by-Step Solution: Step 1: Difference from 24.3 to 23.1: 23.1 − 24.3 = −1.2, which is −1.2.Step 2: Difference from 23.1 to 20.7: 20.7 − 23.1 = −2.4, which is −2 * 1.2.Step 3: Difference from 20.7 to 17.1: 17.1 − 20.7 = −3.6, which is −3 * 1.2.Step 4: The pattern so far is subtracting 1.2, then 2.4, then 3.6. These are −1.2, −2 * 1.2 and −3 * 1.2 respectively.Step 5: Following this pattern, the next difference should be −4 * 1.2 = −4.8.Step 6: Subtracting 4.8 from 17.1 gives 17.1 − 4.8 = 12.3.Step 7: However, the given last term is 12.4, not 12.3, so 12.4 breaks the intended pattern. Verification / Alternative check: We can reconstruct the correct sequence if we follow the rule exactly: start from 24.3, subtract 1.2 to get 23.1, subtract 2.4 to get 20.7, subtract 3.6 to get 17.1 and subtract 4.8 to get 12.3. This produces a very clean pattern where each step uses the next integer multiple of 1.2. Since 12.4 does not fit this pattern, it is natural to treat it as the odd one out. Why Other Options Are Wrong: Values 23.1, 20.7 and 17.1 all support the regular sequence of differences. Removing any of them would break the clear progression of subtracting 1.2, 2.4 and 3.6. 12.4 is the only value that fails to be exactly one of these expected steps away from the preceding term. Common Pitfalls: Since the discrepancy between 12.3 and 12.4 is very small, some students may overlook it and assume rounding. However, competitive exams often expect exact adherence to a numerical pattern. Paying close attention to decimal differences is important when working with series that use decimal step sizes. Final Answer: The term that does not fit the consistent difference pattern and is therefore the odd one out is 12.4.

Question 15

In the series 1000, 1012, 988, 1024, 978, which number is the odd man out if the intended pattern is to add and subtract increasing multiples of 12?

Accepted Answer

Introduction / Context: This series alternates between rising and falling values: 1000, 1012, 988, 1024, 978. The jumps between terms suggest a pattern involving fixed multiples of 12, with the magnitude of the multiple increasing step by step. Our task is to see which term does not fit this add and subtract structure. Given Data / Assumptions: The terms of the series are: 1000 1012 988 1024 978 We assume that the intended pattern is to alternately add and subtract multiples of 12, with the multiples being 12, 24, 36 and 48 in order. Concept / Approach: We will compute the differences between consecutive terms and check whether these differences match ±12, ±24, ±36 and ±48. If four steps follow this rule and one does not, then the term involved in the incorrect step is the odd one out. Step-by-Step Solution: Step 1: From 1000 to 1012 the change is 1012 − 1000 = +12, which is +1 * 12.Step 2: From 1012 to 988 the change is 988 − 1012 = −24, which is −2 * 12.Step 3: From 988 to 1024 the change is 1024 − 988 = +36, which is +3 * 12.Step 4: Up to this point, we have added 12, subtracted 24 and added 36, so the next logical step is to subtract 48 (that is −4 * 12).Step 5: Subtracting 48 from 1024 gives 1024 − 48 = 976.Step 6: However, the given last term is 978, not 976, so 978 does not fit the pattern of adding and subtracting exact multiples of 12. Verification / Alternative check: We can reconstruct the intended series if no error is present. Starting from 1000 and applying the steps +12, −24, +36 and −48 gives 1000, 1012, 988, 1024 and 976. This sequence obeys the rule of alternately adding and subtracting increasing multiples of 12. Comparing this to the given series shows that all terms match except the last value, which should be 976 rather than 978. Why Other Options Are Wrong: The intermediate terms 1012, 988 and 1024 all fit the exactly computed differences of +12, −24 and +36. The starting term 1000 is fixed. Only the final term, 978, fails to be exactly 48 less than 1024, so it is the only one that breaks the rule. Therefore 978 must be the odd one out. Common Pitfalls: Because 978 is close to 976, it is easy to overlook the error and think that rounding or an approximate pattern is intended. However, number series questions usually rely on exact arithmetic, especially when dealing with clean multiples such as 12, 24, 36 and 48. Always check differences precisely rather than estimating. Final Answer: The number that does not follow the alternating plus and minus multiples of 12 pattern is 978.

Question 16

In the number series 8, 14, 24, 60 and 180, which one number is the odd man out because it does not follow the same simple divisibility pattern as the others?

Accepted Answer

Introduction / Context: This problem asks you to identify the odd man out in a short numerical series. Such questions usually rely on a very simple number property such as divisibility, parity, or being a multiple of a fixed integer. Spotting these properties quickly is very useful in aptitude exams where speed matters. Given Data / Assumptions: The given terms of the series are: 8 14 24 60 180 Exactly one number is assumed to violate a clear divisibility pattern shared by the others. Concept / Approach: A quick way to attack an odd man out question is to check divisibility by small integers such as 2, 3, 4, 5, and so on. Here, all numbers are even, so we go one step further and test divisibility by 4, since many aptitude questions use this simple rule. The number that fails the shared property is the odd one out. Step-by-Step Solution: Step 1: Test divisibility by 4 using the standard rule. A number is divisible by 4 if the last two digits form a number divisible by 4.Step 2: Check 8. It is 4 * 2, so it is divisible by 4.Step 3: Check 24. It is 4 * 6, so it is divisible by 4.Step 4: Check 60. The last two digits 60 give 60 / 4 = 15, so 60 is divisible by 4.Step 5: Check 180. The last two digits 80 give 80 / 4 = 20, so 180 is also divisible by 4.Step 6: Check 14. The last two digits 14 give 14 / 4 = 3.5, which is not an integer, so 14 is not divisible by 4. Verification / Alternative check: We can factor each number to double check: 8 = 2^3, 24 = 2^3 * 3, 60 = 2^2 * 3 * 5, and 180 = 2^2 * 3^2 * 5, all of which contain at least two factors of 2 and so are multiples of 4. But 14 = 2 * 7 has only one factor 2, so it is not a multiple of 4. This confirms that 14 does not share the same divisibility property as the others. Why Other Options Are Wrong: 180, 60 and 24 all share the property of being divisible by 4 as well as by 2. They fit naturally into a group of numbers that are multiples of 4. Removing any of them would leave 14 still standing out as non divisible by 4, so they cannot be considered the correct odd man out. Common Pitfalls: Candidates sometimes overthink such questions and search for complicated patterns involving multiplication or powers. In exam settings it is important to first check very simple properties like divisibility or parity. Once you notice that only 14 fails the divisibility by 4 test, the answer becomes straightforward. Final Answer: The number that does not share the common divisibility pattern is 14.

Question 17

In the following list of two letter combinations MN, NM, OL and ET, which pair of letters is the odd one out based on the numerical positions of the letters in the English alphabet?

Accepted Answer

Introduction / Context: This question is about finding the odd pair of letters from the given combinations. Instead of numbers, we work with alphabet positions. Such questions check your ability to translate letters into their numerical positions in the alphabet and then look for a consistent numerical pattern. Given Data / Assumptions: The given two letter combinations are: MN NM OL ET We assume that exactly one pair does not satisfy the same numerical relationship between the positions of its letters. Concept / Approach: The English alphabet positions are A = 1, B = 2, ..., Z = 26. A useful idea here is to add the positions of the two letters in each pair and see whether most of the sums are the same. The pair whose sum is different from the common value is the odd one out. Step-by-Step Solution: Step 1: Find the alphabetical positions of each letter.M is the 13th letter and N is the 14th letter, so MN has positions 13 and 14.Step 2: Compute the sum for MN: 13 + 14 = 27.Step 3: For NM, the letters are N (14) and M (13), giving 14 + 13 = 27 again.Step 4: For OL, O is 15 and L is 12, giving 15 + 12 = 27.Step 5: For ET, E is 5 and T is 20, giving 5 + 20 = 25.Step 6: We see that MN, NM and OL all have letter position sums equal to 27, but ET has a sum equal to 25. Verification / Alternative check: You can verify by listing the three pairs MN, NM and OL as mirror pairs around the middle of the alphabet because their positions always add up to 27. For example, the pair (13, 14) is just reversed in NM. ET does not share this mirror sum, and 25 is clearly distinct from 27. This reinforces that ET is the only pair not following the same rule. Why Other Options Are Wrong: MN, NM and OL all belong to the special group of letter pairs whose positions add up to 27. Removing any of them as the odd one would ignore this neat and consistent property. Therefore, they should be considered similar, and ET should be singled out as different. Common Pitfalls: Some learners may search for patterns like letters being consecutive, reversed or symmetric, and overlook the simple and very strong pattern in the sums of positions. Whenever you see letter pairs, checking position sums is a powerful and quick technique to find the odd one out. Final Answer: The pair of letters that does not follow the common sum of positions pattern is ET.

Question 18

Among the numbers 3, 24, 186, 1008, 5040 and 20160, which one is the odd man out because its prime factorization includes a larger prime that does not appear in the others?

Accepted Answer

Introduction / Context: This is an odd man out question that focuses on properties of prime factorization. Instead of looking for arithmetic progressions or series formulas, you need to examine which prime numbers appear in the factors of each term and identify the one that includes a different type of prime factor. Given Data / Assumptions: The list of numbers is: 3 24 186 1008 5040 20160 We assume that five of these numbers have prime factors drawn only from a small set of primes, while one number introduces a larger prime that does not appear in any other factorization. Concept / Approach: Prime factorization is the expression of a number as a product of prime numbers. To solve this question, we factor each number and observe which primes are used. If all but one number can be expressed using only the primes 2, 3, 5 and 7, then the number that needs an additional larger prime will be the odd one out. Step-by-Step Solution: Step 1: Factor 3. It is already a prime number, so 3 = 3.Step 2: Factor 24. We have 24 = 2^3 * 3.Step 3: Factor 186. We get 186 = 2 * 3 * 31, which introduces the prime 31.Step 4: Factor 1008. One way is 1008 = 16 * 63 = 2^4 * 3^2 * 7.Step 5: Factor 5040. A standard factorization is 5040 = 2^4 * 3^2 * 5 * 7.Step 6: Factor 20160. We can see 20160 = 4 * 5040 = 2^6 * 3^2 * 5 * 7.Step 7: Observe the primes used. The numbers 3, 24, 1008, 5040 and 20160 use only the primes 2, 3, 5 and 7. However, 186 uses the larger prime 31 in addition to 2 and 3. Verification / Alternative check: To verify, list the prime sets explicitly: 3 uses {3}, 24 uses {2, 3}, 1008 uses {2, 3, 7}, 5040 and 20160 use {2, 3, 5, 7}, and 186 uses {2, 3, 31}. The only number that requires a prime greater than 7 is 186. This makes it stand out from the rest of the list. Why Other Options Are Wrong: The numbers 24, 20160 and 5040 all have prime factors limited to 2, 3, 5 and 7. They are highly composite and share similar factor patterns. Removing any one of them as the odd man out would leave 186 still distinguished by its use of the prime 31, so they cannot be the correct choices. Common Pitfalls: Students may initially search for patterns in the ratios or differences between consecutive numbers and become frustrated. However, not every sequence is meant to be analyzed as a progression; some rely entirely on factorization. Remember that odd man out questions often use prime factors as a hidden but straightforward clue. Final Answer: The number whose prime factors include the additional prime 31 and which therefore is the odd man out is 186.

Question 19

Find the next number in the number series 1, 4, 12, 32, ? by identifying the pattern of doubling and adding growing powers of 2.

Accepted Answer

Introduction / Context: This question gives a number series and asks you to determine the next term. The terms grow quite quickly: 1, 4, 12, 32, ?. Recognizing how each term is obtained from the previous one, especially using multiplication and powers of 2, is essential for solving many number series questions in aptitude tests. Given Data / Assumptions: The series is: 1 4 12 32 ? We assume a consistent rule that uses basic operations such as multiplication and addition, without any hidden or overly complex functions. Concept / Approach: When numbers grow quite fast but not purely by a constant multiplier, a useful approach is to check whether each term is obtained by doubling the previous term and then adding a quantity that also follows a pattern. In this series, the extra quantities added after doubling turn out to be powers of 2 that also increase systematically. Step-by-Step Solution: Step 1: Move from 1 to 4. Check 1 * 2 + 2 = 4. Here, we double 1 and add 2.Step 2: Move from 4 to 12. Check 4 * 2 + 4 = 12. We double 4 and add 4.Step 3: Move from 12 to 32. Check 12 * 2 + 8 = 32. We double 12 and add 8.Step 4: Observe the added numbers: 2, 4, 8. These are powers of 2, namely 2^1, 2^2 and 2^3.Step 5: The pattern suggests that the next term is found by again doubling the previous term and adding the next power of 2, which is 2^4 = 16.Step 6: Therefore, the next term should be 32 * 2 + 16 = 64 + 16 = 80. Verification / Alternative check: We can restate the sequence as: a(1) = 1, and for n ≥ 2, a(n) = 2 * a(n - 1) + 2^(n - 1). Applying this formula: a(2) = 2 * 1 + 2^1 = 4, a(3) = 2 * 4 + 2^2 = 12, a(4) = 2 * 12 + 2^3 = 32, and a(5) = 2 * 32 + 2^4 = 80. This confirms that 80 is the unique correct continuation. Why Other Options Are Wrong: 100, 192 and 169 do not satisfy the consistent rule of doubling and adding successive powers of 2. For example, 100 would require adding 36 after doubling 32, and 36 does not fit into the neat sequence 2, 4, 8, 16. Therefore, those options are not logically supported by the pattern in the given terms. Common Pitfalls: Some students look only at differences between terms (3, 8, 20) and do not realize that these differences themselves are related to powers of 2. Others might guess from approximate growth instead of verifying a precise rule. Always try to check both multiplication and a secondary addition when growth is not purely geometric. Final Answer: The next number in the series, following the pattern of doubling and adding powers of 2, is 80.

Question 20

In the number series 0, 3, 8, 15, 24, ?, determine the next term by recognizing the pattern related to squares of natural numbers.

Accepted Answer

Introduction / Context: This question presents a sequence of numbers that gradually increases: 0, 3, 8, 15, 24, ?. The task is to find the next term in the series. These numbers look very close to perfect squares, which is a strong clue that the series might be constructed using simple square numbers of consecutive integers. Given Data / Assumptions: The terms given are: 0 3 8 15 24 ? We assume a simple and consistent rule, very likely involving n^2 for small integer values of n, adjusted by a fixed quantity. Concept / Approach: A good way to approach this kind of problem is to compare each term with square numbers of 1, 2, 3, 4, 5, 6, and so on. If the difference between each term and the square shows a consistent pattern, we can use that pattern to find the next number. Here, the pattern turns out to be n^2 - 1. Step-by-Step Solution: Step 1: Check the first term. For n = 1, n^2 - 1 = 1^2 - 1 = 0, which matches the first term.Step 2: Check the second term. For n = 2, n^2 - 1 = 2^2 - 1 = 4 - 1 = 3, which matches the second term.Step 3: Check the third term. For n = 3, n^2 - 1 = 9 - 1 = 8, matching the third term.Step 4: Check the fourth term. For n = 4, n^2 - 1 = 16 - 1 = 15, matching the fourth term.Step 5: Check the fifth term. For n = 5, n^2 - 1 = 25 - 1 = 24, matching the fifth term.Step 6: For the sixth position, we take n = 6. Then n^2 - 1 = 36 - 1 = 35. This should be the next term. Verification / Alternative check: The general term of the sequence can be written as a(n) = n^2 - 1 for n = 1, 2, 3, 4, 5, 6. Substituting n = 1 to 5 reproduces all the given terms exactly, so extending it to n = 6 gives a(6) = 35 without any contradiction. Because the pattern is simple and exact, this strongly confirms our answer. Why Other Options Are Wrong: Values like 34, 36 and 37 do not equal n^2 - 1 for n = 6. Specifically, 36 is equal to 6^2, 34 is 36 - 2, and 37 is 36 + 1. Choosing any of them would break the simple and elegant square minus one pattern that fits all previous terms perfectly. Common Pitfalls: Some candidates may look only at the differences 3, 5, 7, 9 and decide the next difference should be 11, giving 24 + 11 = 35. Interestingly, this reasoning also leads to 35, because the differences form consecutive odd numbers. However, recognizing the deeper structure as n^2 - 1 helps confirm the result more confidently and is useful in similar problems involving square numbers. Final Answer: The next number in the series, following the pattern a(n) = n^2 - 1, is 35.

Odd Man Out and Series Questions