Series

Ladakh Prison Department · Reasoning · 44 practice questions with answers and explanations: 22 Easy, 21 Medium, 1 Hard.

Sample questions

Sample Easy question 1

Find the next number: 5, 9, 13, 17, ?

  1. 21
  2. 19
  3. 20
  4. 23
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Answer: A. Simple arithmetic progression, add 4 each time: 17 + 4 = 21.

Sample Easy question 2

Find the next number: 3, 6, 12, 24, ?

  1. 46
  2. 36
  3. 48
  4. 42
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Answer: C. Geometric progression, each term doubles: 24 × 2 = 48.

Sample Easy question 3

Find the missing number: 8, 14, ?, 26, 32

  1. 22
  2. 20
  3. 18
  4. 19
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Answer: B. The series increases by 6 each time: 14 + 6 = 20 (check: 20 + 6 = 26).

Sample Medium question 4

Find the odd one out: 5, 10, 17, 27, 37, 50

  1. 37
  2. 50
  3. 17
  4. 27
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Answer: D. The correct pattern is n² + 1 for n = 2, 3, 4, 5, 6, 7: 5, 10, 17, 26, 37, 50. The term 27 breaks this pattern; it should be 26 (5² + 1).

Sample Medium question 5

In this interleaved series, find the next term: 3, 100, 7, 90, 11, 80, ?

  1. 75
  2. 70
  3. 15
  4. 16
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Answer: C. Two interleaved series: odd positions increase by 4 (3,7,11,15...) and even positions decrease by 10 (100,90,80...); the next term (7th, odd position) is 11 + 4 = 15.

Sample Medium question 6

Find the next letter-number term: C3, F9, I27, L81, ?

  1. P243
  2. N243
  3. O162
  4. O243
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Answer: D. Letters skip two each time (C,F,I,L,O) and the number is multiplied by 3 each time (3,9,27,81,243), giving O243.

Sample Hard question 7

Find the next number: 2, 5, 14, 41, ?

  1. 124
  2. 122
  3. 128
  4. 120
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Answer: B. Each term follows (previous × 3) - 1: 41 × 3 - 1 = 122.

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