Next CSE-PPT: 14 March 2027 · Professional & Subprofessional
Civil Service Exam reviewer on number and letter series, number and letter analogies, odd-one-out items and letter codes, with every pattern checked by script.
Series and analogy questions test whether you can find a rule and apply it. Number series may add, subtract, multiply or use squares and primes; letter series often move forward or backward with growing gaps; analogies ask you to apply the rule from one pair to another.
Write the alphabet with its position numbers (A = 1, B = 2, …, Z = 26) on your scratch paper. For number series, look at the differences first, then the ratios, then squares and cubes. Every answer here was checked by script.
Correct answer: A. HJL
Each letter of ACE moves forward one place to give BDF (A→B, C→D, E→F). Applying the same rule to GIK gives HJL. Note that ACE and GIK both skip one letter between letters, so the answer should too.
Read detailsCorrect answer: A. DW
The first letter moves forward one place (A→B, so C→D) and the second moves back one place (Z→Y, so X→W). The answer is DW. Note that A and Z, B and Y, C and X, D and W are mirror pairs from the two ends of the alphabet.
Read detailsCorrect answer: A. EPH
Each letter of CAT moves forward one place to give DBU. Doing the same to DOG gives EPH (D→E, O→P, G→H). Shift codes like this are common in coding-decoding questions.
Read detailsCorrect answer: C. 64
27 is 3 cubed (3 × 3 × 3). Applying the same rule, 4 cubed is 4 × 4 × 4 = 64. The option 16 is 4 squared, which uses the wrong rule.
Read detailsCorrect answer: C. 50
26 = 5² + 1. Applying the same rule, 7² + 1 = 49 + 1 = 50. Always test the rule on the given pair before applying it. The option 49 is 7² without the +1.
Read detailsCorrect answer: B. 8
3 is the square root of 9. Applying the same rule, the square root of 64 is 8, since 8 × 8 = 64. The option 32 is half of 64, which does not match the rule for 9 and 3.
Read detailsCorrect answer: B. V
The gaps between letters grow by one each time: B→D (+2), D→G (+3), G→K (+4), K→P (+5). The next gap is +6, so P→V. Writing the position numbers (2, 4, 7, 11, 16) makes the growing gaps easy to see.
Read detailsCorrect answer: B. L
The series moves backwards with growing gaps: Z→X (−2), X→U (−3), U→Q (−4). The next gap is −5, so Q→L. The position numbers are 26, 24, 21, 17, 12.
Read detailsCorrect answer: B. MN
Each pair is two consecutive letters, and each pair starts three letters after the previous one: A, D, G, J, so the next starts with M. The answer is MN.
Read detailsCorrect answer: B. X
Two series alternate: A, B, C moving forward from the start of the alphabet, and Z, Y moving backward from the end. The next letter belongs to the second series: X.
Read detailsCorrect answer: C. 38
Each term is a perfect square plus two: 1 + 2, 4 + 2, 9 + 2, 16 + 2, 25 + 2, so the next is 36 + 2 = 38. The differences 3, 5, 7, 9, 11 (odd numbers) confirm the pattern.
Read detailsCorrect answer: C. 91
The differences are 4, 9, 16 and 25, which are perfect squares (2², 3², 4², 5²). The next difference is 6² = 36, so 55 + 36 = 91. Each term is the sum of the squares from 1² up to that point.
Read detailsCorrect answer: D. 720
Each term is the previous term multiplied by the next whole number: ×2, ×3, ×4, ×5. The next step is ×6, so 120 × 6 = 720. When terms grow very quickly, test multiplication by changing numbers.
Read detailsCorrect answer: C. 768
Each term is four times the one before: 3 × 4 = 12, 12 × 4 = 48, 48 × 4 = 192, so the next is 192 × 4 = 768. The ratio between terms stays the same, which makes this a geometric series.
Read detailsCorrect answer: D. 1440
The multipliers increase by one each time: ×2, ×3, ×4, ×5. The next multiplier is 6, so 240 × 6 = 1,440. Dividing each term by the one before it reveals the changing multiplier.
Read detailsCorrect answer: C. 52
The differences are 3, 6, 9 and 12, which go up by 3 each time. The next difference is 15, so 37 + 15 = 52. A series whose differences form their own simple series is called a second-level series.
Read detailsCorrect answer: D. 48
All the other numbers are perfect squares: 16 = 4², 25 = 5², 36 = 6² and 49 = 7². The number 48 is not a perfect square, so it is the odd one out.
Read detailsCorrect answer: C. 9
All the others are prime numbers. The number 9 can be divided by 3 (9 = 3 × 3), so it is not prime. All five are odd, so oddness is not the rule here.
Read detailsCorrect answer: D. MOP
BCD, FGH and JKL are each three consecutive letters of the alphabet. In MOP, the letter N is skipped between M and O, so it does not follow the pattern.
Read detailsCorrect answer: A. FLWB
Each letter moves forward three places: R→U, O→R, A→D, D→G. Applying the same shift to CITY gives C→F, I→L, T→W, Y→B (wrapping around after Z). The answer is FLWB.
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