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Number & Letter Series aptitude questions

Find the rule, then the missing term.

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Formula sheetNumber & Letter Series: the essentialsFormula sheetNumber & Letter Series: the essentialsShow

Find the rule in this order, and confirm it on every term before extending.

  1. Differences. Write them under the terms; if they vary, take second differences. A constant second difference means a quadratic such as n² + 1 or n(n + 1).
  2. Ratios. A constant ratio is geometric; rising multipliers (×2, ×3, ×4) point to factorial-like growth.
  3. Double and adjust. Terms that roughly double often follow 'previous × 2 + 1', as in 3, 7, 15, 31.
  4. Known sequences. Squares, cubes, primes, Fibonacci (each term the sum of the two before) and near misses such as n² − 1 or n³ + 1.
  5. Alternation. If the differences zig-zag, split odd and even positions into two series, or look for two operations taking turns.
  6. Digits. When the arithmetic fails, read the digits: 13, 35, 57, 79, 911 joins consecutive odd numbers.

Letters and odd ones out

  • Convert letters to positions, A = 1 to Z = 26, and back at the end. Landmarks: E 5, J 10, O 15, T 20, Y 25. The opposite of the nth letter is the (27 − n)th.
  • In pairs such as AZ, BY, CX, treat each position as its own series.
  • For an odd one out, test squares, cubes and primes first; exactly one term should break the rule.

Example: 5, 8, 13, 20, 29 has differences 3, 5, 7, 9, so the next term is 29 + 11 = 40 (n² + 4).

Questions53

1

2, 5, 10, 17, 26, ?

Find the next term: 2, 5, 10, 17, 26, ?

differences

45s

Easy2

3, 7, 15, 31, 63, ?

Find the next term: 3, 7, 15, 31, 63, ?

multiplicative

45s

Easy3

5, 11, 8, 14, 11, ?

Find the next term: 5, 11, 8, 14, 11, ?

alternating

60s

Medium4

A, D, G, J, ?

Find the next letter: A, D, G, J, ?

letters

45s

Easy5

4, 6, 10, 16, 26, ?

Find the next term: 4, 6, 10, 16, 26, ?

fibonacci

45s

Medium6

The number that does not belong

Which number does not belong in this series? 8, 27, 64, 100, 125, 216

odd one out

45s

Easy7

2, 6, 12, 20, 30, ?

Find the next term: 2, 6, 12, 20, 30, ?

differences

45s

Easy8

1, 4, 9, 16, 25, ?

Find the next term: 1, 4, 9, 16, 25, ?

squares

30s

Easy9

1, 8, 27, 64, ?

Find the next term: 1, 8, 27, 64, ?

cubes

30s

Easy10

1, 9, 25, 49, ?

Find the next term: 1, 9, 25, 49, ?

squares

45s

Easy11

3, 8, 15, 24, 35, ?

Find the next term: 3, 8, 15, 24, 35, ?

squares

45s

Easy12

7, 26, 63, 124, ?

Find the next term: 7, 26, 63, 124, ?

cubes

60s

Medium13

336, 210, 120, 60, 24, ?

Find the next term: 336, 210, 120, 60, 24, ?

cubes

105s

Hard14

2, 12, 36, 80, ?

Find the next term: 2, 12, 36, 80, ?

cubes

120s

Hard15

3, 6, 11, 18, 27, ?

Find the next term: 3, 6, 11, 18, 27, ?

differences

45s

Easy16

4, 7, 12, 19, 28, ?

Find the next term: 4, 7, 12, 19, 28, ?

differences

45s

Easy17

2, 7, 14, 23, 34, ?

Find the next term: 2, 7, 14, 23, 34, ?

differences

45s

Easy18

5, 9, 17, 29, 45, ?

Find the next term: 5, 9, 17, 29, 45, ?

differences

45s

Medium19

6, 11, 21, 36, 56, ?

Find the next term: 6, 11, 21, 36, 56, ?

differences

45s

Medium20

6, 12, 21, 33, ?

Find the next term: 6, 12, 21, 33, ?

differences

45s

Easy21

120, 99, 80, 63, 48, ?

Find the next term: 120, 99, 80, 63, 48, ?

differences

75s

Medium22

20, 19, 17, 14, 10, ?

Find the next term: 20, 19, 17, 14, 10, ?

differences

45s

Easy23

1, 3, 7, 15, 31, ?

Find the next term: 1, 3, 7, 15, 31, ?

multiplicative

45s

Easy24

15, 31, 63, 127, 255, ?

Find the next term: 15, 31, 63, 127, 255, ?

multiplicative

45s

Easy25

2, 5, 11, 23, 47, ?

Find the next term: 2, 5, 11, 23, 47, ?

multiplicative

45s

Easy26

5, 11, 24, 51, 106, ?

Find the next term: 5, 11, 24, 51, 106, ?

multiplicative

105s

Hard27

9, 27, 31, 155, 161, ?

Find the next term: 9, 27, 31, 155, 161, ?

alternating

120s

Hard28

8, 24, 12, 36, 18, ?

Find the next term: 8, 24, 12, 36, 18, ?

alternating

60s

Medium29

100, 50, 52, 26, 28, ?

Find the next term: 100, 50, 52, 26, 28, ?

alternating

60s

Medium30

48, 24, 96, 48, 192, ?

Find the next term: 48, 24, 96, 48, 192, ?

alternating

60s

Medium31

7, 10, 8, 11, 9, ?

Find the next term: 7, 10, 8, 11, 9, ?

alternating

45s

Easy32

22, 21, 23, 22, 24, 23, ?

Find the next term: 22, 21, 23, 22, 24, 23, ?

alternating

75s

Medium33

1, 1, 2, 3, 5, 8, ?

Find the next term: 1, 1, 2, 3, 5, 8, ?

fibonacci

30s

Easy34

0, 2, 6, 12, 20, ?

Find the next term: 0, 2, 6, 12, 20, ?

differences

45s

Easy35

1, 5, 14, 30, 55, ?

Find the next term: 1, 5, 14, 30, 55, ?

differences · squares

90s

Hard36

1, 2, 6, 24, 120, ?

Find the next term: 1, 2, 6, 24, 120, ?

factorial

60s

Medium37

2, 4, 12, 48, ?

Find the next term: 2, 4, 12, 48, ?

multiplicative

60s

Medium38

240, 120, 40, 10, ?

Find the next term: 240, 120, 40, 10, ?

multiplicative

60s

Medium39

1, 2, 4, 8, 16, ?

Find the next term: 1, 2, 4, 8, 16, ?

multiplicative

30s

Easy40

5, 10, 20, 40, ?

Find the next term: 5, 10, 20, 40, ?

multiplicative

30s

Easy41

3, 12, 27, 48, ?

Find the next term: 3, 12, 27, 48, ?

squares

60s

Medium42

2, 3, 5, 7, 11, ?

Find the next term: 2, 3, 5, 7, 11, ?

primes

30s

Easy43

11, 13, 17, 19, 23, ?

Find the next term: 11, 13, 17, 19, 23, ?

primes

45s

Easy44

10, 100, 200, 310, ?

Find the next term: 10, 100, 200, 310, ?

differences

45s

Medium45

13, 35, 57, 79, 911, ?

Find the next term: 13, 35, 57, 79, 911, ?

digits

105s

Hard46

B, D, F, H, ?

Find the next letter: B, D, F, H, ?

letters

45s

Easy47

B, E, H, K, ?

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

letters

45s

Easy48

A, C, F, J, ?

Find the next letter: A, C, F, J, ?

letters

60s

Medium49

Z, X, V, T, ?

Find the next letter: Z, X, V, T, ?

letters

45s

Easy50

AZ, BY, CX, ?

Find the next pair: AZ, BY, CX, ?

letters

45s

MediumLoad 3 more

Showing 50 of 53

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Number & Letter Series Aptitude Questions with Solutions

53 Number & Letter Series questions with hints, worked solutions and time targets — 29 easy · 18 medium · 6 hard. Find the rule, then the missing term.

  • Section: Logical Reasoning
  • Questions: 53
  • By difficulty: 29 easy · 18 medium · 6 hard
  • Cost: Free, unlimited on every plan

Find the rule, then the missing term.

Number & Letter Series: the essentials

Find the rule in this order, and confirm it on every term before extending.

  1. Differences. Write them under the terms; if they vary, take second differences. A constant second difference means a quadratic such as n² + 1 or n(n + 1).
  2. Ratios. A constant ratio is geometric; rising multipliers (×2, ×3, ×4) point to factorial-like growth.
  3. Double and adjust. Terms that roughly double often follow 'previous × 2 + 1', as in 3, 7, 15, 31.
  4. Known sequences. Squares, cubes, primes, Fibonacci (each term the sum of the two before) and near misses such as n² − 1 or n³ + 1.
  5. Alternation. If the differences zig-zag, split odd and even positions into two series, or look for two operations taking turns.
  6. Digits. When the arithmetic fails, read the digits: 13, 35, 57, 79, 911 joins consecutive odd numbers.

Letters and odd ones out

  • Convert letters to positions, A = 1 to Z = 26, and back at the end. Landmarks: E 5, J 10, O 15, T 20, Y 25. The opposite of the nth letter is the (27 − n)th.
  • In pairs such as AZ, BY, CX, treat each position as its own series.
  • For an odd one out, test squares, cubes and primes first; exactly one term should break the rule.

Example: 5, 8, 13, 20, 29 has differences 3, 5, 7, 9, so the next term is 29 + 11 = 40 (n² + 4).

Questions

  1. 2, 5, 10, 17, 26, ? Easy
    Find the next term: 2, 5, 10, 17, 26, ?
  2. 3, 7, 15, 31, 63, ? Easy
    Find the next term: 3, 7, 15, 31, 63, ?
  3. 5, 11, 8, 14, 11, ? Medium
    Find the next term: 5, 11, 8, 14, 11, ?
  4. A, D, G, J, ? Easy
    Find the next letter: A, D, G, J, ?
  5. 4, 6, 10, 16, 26, ? Medium
    Find the next term: 4, 6, 10, 16, 26, ?
  6. The number that does not belong Easy
    Which number does not belong in this series? 8, 27, 64, 100, 125, 216
  7. 2, 6, 12, 20, 30, ? Easy
    Find the next term: 2, 6, 12, 20, 30, ?
  8. 1, 4, 9, 16, 25, ? Easy
    Find the next term: 1, 4, 9, 16, 25, ?
  9. 1, 8, 27, 64, ? Easy
    Find the next term: 1, 8, 27, 64, ?
  10. 1, 9, 25, 49, ? Easy
    Find the next term: 1, 9, 25, 49, ?
  11. 3, 8, 15, 24, 35, ? Easy
    Find the next term: 3, 8, 15, 24, 35, ?
  12. 7, 26, 63, 124, ? Medium
    Find the next term: 7, 26, 63, 124, ?
  13. 336, 210, 120, 60, 24, ? Hard
    Find the next term: 336, 210, 120, 60, 24, ?
  14. 2, 12, 36, 80, ? Hard
    Find the next term: 2, 12, 36, 80, ?
  15. 3, 6, 11, 18, 27, ? Easy
    Find the next term: 3, 6, 11, 18, 27, ?
  16. 4, 7, 12, 19, 28, ? Easy
    Find the next term: 4, 7, 12, 19, 28, ?
  17. 2, 7, 14, 23, 34, ? Easy
    Find the next term: 2, 7, 14, 23, 34, ?
  18. 5, 9, 17, 29, 45, ? Medium
    Find the next term: 5, 9, 17, 29, 45, ?
  19. 6, 11, 21, 36, 56, ? Medium
    Find the next term: 6, 11, 21, 36, 56, ?
  20. 6, 12, 21, 33, ? Easy
    Find the next term: 6, 12, 21, 33, ?
  21. 120, 99, 80, 63, 48, ? Medium
    Find the next term: 120, 99, 80, 63, 48, ?
  22. 20, 19, 17, 14, 10, ? Easy
    Find the next term: 20, 19, 17, 14, 10, ?
  23. 1, 3, 7, 15, 31, ? Easy
    Find the next term: 1, 3, 7, 15, 31, ?
  24. 15, 31, 63, 127, 255, ? Easy
    Find the next term: 15, 31, 63, 127, 255, ?
  25. 2, 5, 11, 23, 47, ? Easy
    Find the next term: 2, 5, 11, 23, 47, ?
  26. 5, 11, 24, 51, 106, ? Hard
    Find the next term: 5, 11, 24, 51, 106, ?
  27. 9, 27, 31, 155, 161, ? Hard
    Find the next term: 9, 27, 31, 155, 161, ?
  28. 8, 24, 12, 36, 18, ? Medium
    Find the next term: 8, 24, 12, 36, 18, ?
  29. 100, 50, 52, 26, 28, ? Medium
    Find the next term: 100, 50, 52, 26, 28, ?
  30. 48, 24, 96, 48, 192, ? Medium
    Find the next term: 48, 24, 96, 48, 192, ?
  31. 7, 10, 8, 11, 9, ? Easy
    Find the next term: 7, 10, 8, 11, 9, ?
  32. 22, 21, 23, 22, 24, 23, ? Medium
    Find the next term: 22, 21, 23, 22, 24, 23, ?
  33. 1, 1, 2, 3, 5, 8, ? Easy
    Find the next term: 1, 1, 2, 3, 5, 8, ?
  34. 0, 2, 6, 12, 20, ? Easy
    Find the next term: 0, 2, 6, 12, 20, ?
  35. 1, 5, 14, 30, 55, ? Hard
    Find the next term: 1, 5, 14, 30, 55, ?
  36. 1, 2, 6, 24, 120, ? Medium
    Find the next term: 1, 2, 6, 24, 120, ?
  37. 2, 4, 12, 48, ? Medium
    Find the next term: 2, 4, 12, 48, ?
  38. 240, 120, 40, 10, ? Medium
    Find the next term: 240, 120, 40, 10, ?
  39. 1, 2, 4, 8, 16, ? Easy
    Find the next term: 1, 2, 4, 8, 16, ?
  40. 5, 10, 20, 40, ? Easy
    Find the next term: 5, 10, 20, 40, ?
  41. 3, 12, 27, 48, ? Medium
    Find the next term: 3, 12, 27, 48, ?
  42. 2, 3, 5, 7, 11, ? Easy
    Find the next term: 2, 3, 5, 7, 11, ?
  43. 11, 13, 17, 19, 23, ? Easy
    Find the next term: 11, 13, 17, 19, 23, ?
  44. 10, 100, 200, 310, ? Medium
    Find the next term: 10, 100, 200, 310, ?
  45. 13, 35, 57, 79, 911, ? Hard
    Find the next term: 13, 35, 57, 79, 911, ?
  46. B, D, F, H, ? Easy
    Find the next letter: B, D, F, H, ?
  47. B, E, H, K, ? Easy
    Find the next letter: B, E, H, K, ?
  48. A, C, F, J, ? Medium
    Find the next letter: A, C, F, J, ?
  49. Z, X, V, T, ? Easy
    Find the next letter: Z, X, V, T, ?
  50. AZ, BY, CX, ? Medium
    Find the next pair: AZ, BY, CX, ?
  51. The odd one out in a list of squares Easy
    Which number does not belong? 4, 9, 16, 24, 36, 49
  52. The odd one out among primes Easy
    Which number does not belong? 17, 23, 29, 33, 41
  53. A term in the middle Medium
    Find the missing term: 3, 7, 15, ?, 63, 127

Placement tests that ask number & letter series