MCQs / Quantitative Reasoning / Number Series

Number Series MCQs — Quantitative Reasoning (page 2)

42 multiple-choice questions on Number Series from Quantitative Reasoning, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

26. Find the next number in the series: 3, 5, 11, 21, 35, ?

  1. 49
  2. 53
  3. 50
  4. 54

Answer: B) 53

Explanation: Differences are 2, 6, 10, 14 — they change by 4 each time, so the next difference is 18: 35 + 18 = 53.

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27. Find the next letter group: AZ, BY, CX, DW, ?

  1. FV
  2. EU
  3. EV
  4. EW

Answer: C) EV

Explanation: First letters go forward A, B, C, D, E; second letters go backward Z, Y, X, W, V.

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28. Find the next letter: B, E, H, K, ?

  1. O
  2. M
  3. L
  4. N

Answer: D) N

Explanation: Each letter is 3 places after the previous one: K (11) + 3 = N (14).

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29. Find the next number in the series: -9, -1, 7, 15, 23, ?

  1. 30
  2. 28
  3. 29
  4. 31

Answer: D) 31

Explanation: Each term increases by 8: 23 + 8 = 31.

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30. Find the next number in the series: 1, 5, 3, 10, 5, 15, ?

  1. 3
  2. 10
  3. 7
  4. 20

Answer: C) 7

Explanation: Two series are mixed together. Odd positions: 1, 3, 5 (step 2); even positions: 5, 10, 15 (step 5). Next is an odd position: 5 + 2 = 7.

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31. Find the next number in the series: 4, 5, 7, 11, 19, ?

  1. 38
  2. 35
  3. 32
  4. 31

Answer: B) 35

Explanation: Rule: multiply by 2 then subtract 3. 19 2 - 3 = 35.

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32. Find the next number in the series: 10, 15, 25, 40, 60, ?

  1. 85
  2. 80
  3. 90
  4. 84

Answer: A) 85

Explanation: Differences are 5, 10, 15, 20 — they change by 5 each time, so the next difference is 25: 60 + 25 = 85.

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33. Find the next number in the series: 2, 6, 12, 20, 30, ?

  1. 48
  2. 42
  3. 40
  4. 41

Answer: B) 42

Explanation: Differences are 4, 6, 8, 10 — they change by 2 each time, so the next difference is 12: 30 + 12 = 42.

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34. Find the next number in the series: 1, 2, 4, 7, 11, ?

  1. 21
  2. 16
  3. 15
  4. 18

Answer: B) 16

Explanation: Differences are 1, 2, 3, 4 — they change by 1 each time, so the next difference is 5: 11 + 5 = 16.

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35. Find the next number in the series: 1, 4, 13, 40, 121, ?

  1. 364
  2. 367
  3. 365
  4. 363

Answer: A) 364

Explanation: Rule: multiply by 3 then add 1. 121 3 + 1 = 364.

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36. Find the next number in the series: 52, 45, 38, 31, 24, ?

  1. 17
  2. 23
  3. 15
  4. 11

Answer: A) 17

Explanation: Each term decreases by 7: 24 - 7 = 17.

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37. Find the next number in the series: 2, 3, 5, 8, 13, 21, ?

  1. 42
  2. 28
  3. 29
  4. 34

Answer: D) 34

Explanation: Each term is the sum of the two before it: 13 + 21 = 34.

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38. Find the next number in the series: 7, 13, 19, 25, 31, ?

  1. 42
  2. 37
  3. 31
  4. 32

Answer: B) 37

Explanation: Each term increases by 6: 31 + 6 = 37.

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39. Find the next number in the series: 10, 17, 26, 37, 50, ?

  1. 65
  2. 64
  3. 67
  4. 69

Answer: A) 65

Explanation: The terms are n^2+1 for n = 3, 4, dots — next is 8^2+1 = 65.

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40. Find the next number in the series: 101, 89, 77, 65, 53, ?

  1. 47
  2. 41
  3. 44
  4. 42

Answer: B) 41

Explanation: Each term decreases by 12: 53 - 12 = 41.

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41. Find the next number in the series: 2, 6, 18, 54, 162, ?

  1. 270
  2. 491
  3. 485
  4. 486

Answer: D) 486

Explanation: Each term is multiplied by 3: 162 3 = 486.

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42. Find the next number in the series: 1024, 512, 256, 128, 64, ?

  1. 29
  2. 36
  3. 32
  4. 30

Answer: C) 32

Explanation: Each term is multiplied by tfrac12: 64 tfrac12 = 32.

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