Number series questions are one of the most common types of problems in competitive exams. They assess your ability to identify patterns in sequences of numbers and predict the next number or missing term in a given series. Below are 60 high-level number series questions with answers, ideal for preparing for exams.
MCQS of Number Series
1. Series: 2, 6, 12, 20, 30, ?
A) 40
B) 42
C) 44
D) 48
Answer: B) 42
Explanation: The differences between consecutive terms are: 4, 6, 8, 10, so the next difference is 12. 30 + 12 = 42.
2. Series: 3, 9, 27, 81, ?
A) 121
B) 243
C) 256
D) 324
Answer: B) 243
Explanation: The series is multiplied by 3 each time (3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81, 81 × 3 = 243).
3. Series: 5, 15, 45, 135, ?
A) 360
B) 405
C) 450
D) 500
Answer: B) 405
Explanation: The series is multiplied by 3 each time (5 × 3 = 15, 15 × 3 = 45, 45 × 3 = 135, 135 × 3 = 405).
4. Series: 1, 4, 9, 16, ?
A) 20
B) 25
C) 30
D) 36
Answer: B) 25
Explanation: The series consists of the square numbers: 1², 2², 3², 4², 5².
5. Series: 2, 4, 8, 16, ?
A) 32
B) 64
C) 24
D) 48
Answer: A) 32
Explanation: The series doubles each time (2 × 2 = 4, 4 × 2 = 8, 8 × 2 = 16, 16 × 2 = 32).
6. Series: 4, 8, 12, 20, ?
A) 28
B) 32
C) 36
D) 40
Answer: B) 32
Explanation: The differences between consecutive terms are: 4, 4, 8, so the next difference is 12. 20 + 12 = 32.
7. Series: 3, 6, 18, 72, ?
A) 180
B) 216
C) 288
D) 324
Answer: B) 216
Explanation: The series is multiplied by 3, then by 3 again (3 × 2 = 6, 6 × 3 = 18, 18 × 4 = 72, 72 × 3 = 216).
8. Series: 1, 2, 6, 24, 120, ?
A) 720
B) 600
C) 480
D) 500
Answer: A) 720
Explanation: The series is the factorial numbers: 1!, 2!, 3!, 4!, 5!.
9. Series: 7, 10, 13, 16, ?
A) 18
B) 17
C) 20
D) 21
Answer: B) 17
Explanation: The differences between consecutive terms are: 3, 3, 3, so the next term is 16 + 3 = 17.
10. Series: 5, 11, 17, 23, ?
A) 29
B) 31
C) 37
D) 41
Answer: A) 29
Explanation: The series increases by 6 each time (5 + 6 = 11, 11 + 6 = 17, 17 + 6 = 23, 23 + 6 = 29).
11. Series: 6, 11, 21, 36, ?
A) 50
B) 52
C) 56
D) 60
Answer: C) 56
Explanation: The differences between consecutive terms are: 5, 10, 15, so the next difference is 20. 36 + 20 = 56.
12. Series: 3, 6, 18, 72, ?
A) 280
B) 300
C) 324
D) 360
Answer: D) 360
Explanation: The series multiplies by 2, then by 3 (3 × 2 = 6, 6 × 3 = 18, 18 × 4 = 72, 72 × 5 = 360).
13. Series: 1, 4, 9, 16, 25, ?
A) 36
B) 50
C) 40
D) 49
Answer: A) 36
Explanation: The series consists of the squares of natural numbers: 1², 2², 3², 4², 5², 6².
14. Series: 6, 10, 16, 24, 34, ?
A) 44
B) 46
C) 48
D) 50
Answer: B) 46
Explanation: The differences are: 4, 6, 8, 10. So, the next difference will be 12. 34 + 12 = 46.
15. Series: 11, 14, 17, 20, ?
A) 23
B) 24
C) 25
D) 26
Answer: A) 23
Explanation: The differences between the terms are constant: 3, so the next term will be 20 + 3 = 23.
16. Series: 2, 5, 11, 23, ?
A) 47
B) 48
C) 49
D) 50
Answer: A) 47
Explanation: The differences between consecutive terms are: 3, 6, 12, so the next difference will be 24. 23 + 24 = 47.
17. Series: 4, 16, 36, 64, ?
A) 96
B) 100
C) 121
D) 144
Answer: B) 100
Explanation: The series is a sequence of squares: 2², 4², 6², 8², 10².
18. Series: 10, 20, 40, 80, ?
A) 160
B) 150
C) 170
D) 180
Answer: A) 160
Explanation: The series doubles each time (10 × 2 = 20, 20 × 2 = 40, 40 × 2 = 80, 80 × 2 = 160).
19. Series: 4, 8, 16, 64, ?
A) 128
B) 256
C) 512
D) 1024
Answer: B) 256
Explanation: The series multiplies by 2, then by 4 (4 × 2 = 8, 8 × 2 = 16, 16 × 4 = 64, 64 × 4 = 256).
20. Series: 5, 13, 29, 61, ?
A) 111
B) 113
C) 119
D) 121
Answer: B) 113
Explanation: The differences between terms are: 8, 16, 32, so the next difference will be 64. 61 + 64 = 113.
21. Series: 1, 2, 4, 8, ?
A) 12
B) 14
C) 16
D) 18
Answer: C) 16
Explanation: The series doubles each time (1 × 2 = 2, 2 × 2 = 4, 4 × 2 = 8, 8 × 2 = 16).
22. Series: 2, 3, 6, 15, ?
A) 40
B) 45
C) 50
D) 60
Answer: B) 45
Explanation: The series follows the pattern: multiply by 1 and add 1, multiply by 2 and add 2, multiply by 3 and add 3, etc.
23. Series: 5, 10, 20, 40, ?
A) 60
B) 80
C) 100
D) 120
Answer: B) 80
Explanation: The series doubles each time (5 × 2 = 10, 10 × 2 = 20, 20 × 2 = 40, 40 × 2 = 80).
24. Series: 3, 9, 27, ?
A) 63
B) 81
C) 96
D) 121
Answer: B) 81
Explanation: The series multiplies by 3 (3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81).
25. Series: 12, 18, 24, 30, ?
A) 34
B) 36
C) 38
D) 40
Answer: B) 36
Explanation: The differences between the terms are: 6, so the next term will be 30 + 6 = 36.
26. Series: 1, 3, 9, 27, ?
A) 72
B) 81
C) 90
D) 120
Answer: B) 81
Explanation: The series multiplies by 3 (1 × 3 = 3, 3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81).
27. Series: 10, 12, 16, 22, ?
A) 28
B) 30
C) 32
D) 34
Answer: A) 28
Explanation: The differences between the terms are: 2, 4, 6, so the next difference is 8. 22 + 8 = 28.
28. Series: 4, 7, 13, 25, ?
A) 50
B) 51
C) 53
D) 55
Answer: B) 51
Explanation: The differences between the terms are: 3, 6, 12, so the next difference is 24. 25 + 24 = 51.
29. Series: 5, 10, 20, 40, 70, ?
A) 100
B) 120
C) 140
D) 150
Answer: C) 140
Explanation: The differences are: 5, 10, 20, 30, so the next difference is 40. 70 + 40 = 140.
30. Series: 2, 5, 10, 17, ?
A) 24
B) 26
C) 28
D) 30
Answer: B) 26
Explanation: The differences between the terms are: 3, 5, 7, so the next difference is 9. 17 + 9 = 26.
31. Series: 1, 4, 10, 20, 35, ?
A) 48
B) 50
C) 52
D) 55
Answer: A) 48
Explanation: The differences between the terms are: 3, 6, 10, 15, so the next difference is 20. 35 + 20 = 48.
32. Series: 3, 12, 48, 192, ?
A) 576
B) 768
C) 768
D) 864
Answer: A) 768
Explanation: The series is multiplied by 4 each time (3 × 4 = 12, 12 × 4 = 48, 48 × 4 = 192, 192 × 4 = 768).
33. Series: 5, 12, 21, 32, ?
A) 43
B) 44
C) 46
D) 48
Answer: B) 44
Explanation: The differences between the terms are: 7, 9, 11, so the next difference is 13. 32 + 13 = 44.
34. Series: 8, 16, 32, 64, ?
A) 128
B) 192
C) 256
D) 512
Answer: A) 128
Explanation: The series doubles each time (8 × 2 = 16, 16 × 2 = 32, 32 × 2 = 64, 64 × 2 = 128).
35. Series: 1, 2, 3, 6, 15, ?
A) 25
B) 30
C) 35
D) 40
Answer: B) 30
Explanation: The series multiplies by the next integer each time: 1 × 2 = 2, 2 × 3 = 6, 6 × 5 = 15, 15 × 2 = 30.
36. Series: 100, 97, 93, 88, ?
A) 85
B) 82
C) 80
D) 75
Answer: B) 82
Explanation: The differences are: -3, -4, -5, so the next difference is -6. 88 – 6 = 82.
37. Series: 3, 10, 21, 36, ?
A) 52
B) 53
C) 60
D) 61
Answer: A) 52
Explanation: The differences are: 7, 11, 15, so the next difference is 19. 36 + 19 = 52.
38. Series: 8, 14, 22, 32, ?
A) 42
B) 43
C) 44
D) 46
Answer: A) 42
Explanation: The differences between terms are: 6, 8, 10, so the next difference is 12. 32 + 12 = 42.
39. Series: 6, 18, 54, 162, ?
A) 243
B) 324
C) 486
D) 512
Answer: A) 243
Explanation: The series is multiplied by 3 each time (6 × 3 = 18, 18 × 3 = 54, 54 × 3 = 162, 162 × 3 = 243).
40. Series: 11, 13, 17, 23, ?
A) 29
B) 31
C) 33
D) 37
Answer: A) 29
Explanation: The series consists of prime numbers: 11, 13, 17, 23, and the next prime number is 29.
41. Series: 4, 8, 16, 24, ?
A) 30
B) 36
C) 40
D) 48
Answer: D) 48
Explanation: The differences are: 4, 8, 8, so the next difference is 16. 24 + 16 = 48.
42. Series: 9, 18, 27, 36, ?
A) 44
B) 45
C) 49
D) 54
Answer: B) 45
Explanation: The differences between terms are: 9, 9, 9, so the next term will be 36 + 9 = 45.
43. Series: 2, 5, 12, 27, ?
A) 55
B) 60
C) 61
D) 62
Answer: C) 61
Explanation: The differences between terms are: 3, 7, 15, so the next difference is 31. 27 + 31 = 61.
44. Series: 8, 12, 16, 24, ?
A) 30
B) 32
C) 34
D) 36
Answer: B) 32
Explanation: The differences between terms are: 4, 4, 8, so the next difference is 8. 24 + 8 = 32.
45. Series: 3, 5, 7, 11, 13, ?
A) 15
B) 17
C) 19
D) 23
Answer: B) 17
Explanation: The series consists of prime numbers: 3, 5, 7, 11, 13, and the next prime number is 17.
46. Series: 3, 6, 12, 24, ?
A) 48
B) 50
C) 54
D) 60
Answer: A) 48
Explanation: The series doubles each time (3 × 2 = 6, 6 × 2 = 12, 12 × 2 = 24, 24 × 2 = 48).
47. Series: 2, 6, 18, 54, ?
A) 162
B) 182
C) 198
D) 225
Answer: A) 162
Explanation: The series is multiplied by 3 each time (2 × 3 = 6, 6 × 3 = 18, 18 × 3 = 54, 54 × 3 = 162).
48. Series: 4, 7, 11, 16, ?
A) 22
B) 21
C) 20
D) 19
Answer: D) 19
Explanation: The differences between the terms are: 3, 4, 5, so the next difference is 6. 16 + 6 = 19.
49. Series: 2, 5, 11, 23, ?
A) 35
B) 47
C) 49
D) 51
Answer: B) 47
Explanation: The differences between terms are: 3, 6, 12, so the next difference is 24. 23 + 24 = 47.
50. Series: 5, 10, 15, 20, ?
A) 25
B) 30
C) 35
D) 40
Answer: A) 25
Explanation: The series increases by 5 each time (5 + 5 = 10, 10 + 5 = 15, 15 + 5 = 20, 20 + 5 = 25).
51. Series: 2, 5, 11, 23, ?
A) 45
B) 47
C) 49
D) 51
Answer: B) 47
Explanation: The differences between terms are: 3, 6, 12, so the next difference is 24. 23 + 24 = 47.
52. Series: 7, 14, 28, 56, ?
A) 77
B) 84
C) 92
D) 112
Answer: B) 84
Explanation: The series doubles each time (7 × 2 = 14, 14 × 2 = 28, 28 × 2 = 56, 56 × 2 = 84).
53. Series: 3, 9, 27, 81, ?
A) 120
B) 126
C) 162
D) 243
Answer: D) 243
Explanation: The series multiplies by 3 each time (3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81, 81 × 3 = 243).
54. Series: 1, 4, 9, 16, ?
A) 20
B) 24
C) 25
D) 28
Answer: C) 25
Explanation: The series consists of perfect squares: 1², 2², 3², 4², 5².
55. Series: 7, 14, 28, 56, ?
A) 70
B) 72
C) 84
D) 100
Answer: C) 84
Explanation: The series doubles each time (7 × 2 = 14, 14 × 2 = 28, 28 × 2 = 56, 56 × 2 = 84).
56. Series: 2, 5, 8, 13, ?
A) 16
B) 18
C) 21
D) 23
Answer: D) 23
Explanation: The differences between terms are: 3, 3, 5, so the next difference is 7. 13 + 7 = 23.
57. Series: 1, 4, 9, 16, ?
A) 22
B) 24
C) 25
D) 28
Answer: C) 25
Explanation: The series is a sequence of perfect squares: 1², 2², 3², 4², 5².
58. Series: 2, 3, 7, 15, ?
A) 30
B) 31
C) 32
D) 33
Answer: B) 31
Explanation: The differences are: 1, 4, 8, so the next difference is 16. 15 + 16 = 31.
59. Series: 3, 6, 12, 24, ?
A) 40
B) 48
C) 50
D) 55
Answer: B) 48
Explanation: The series doubles each time (3 × 2 = 6, 6 × 2 = 12, 12 × 2 = 24, 24 × 2 = 48).
60. Series: 2, 6, 12, 20, ?
A) 30
B) 36
C) 40
D) 42
Answer: A) 30
Explanation: The differences are: 4, 6, 8, so the next difference is 10. 20 + 10 = 30.
61. Series: 1, 4, 16, 64, ?
A) 128
B) 256
C) 512
D) 1024
Answer: B) 256
Explanation: The series multiplies each term by 4 (1 × 4 = 4, 4 × 4 = 16, 16 × 4 = 64, 64 × 4 = 256).
62. Series: 7, 15, 31, 63, ?
A) 127
B) 128
C) 130
D) 140
Answer: A) 127
Explanation: The series follows the pattern: each term is 1 less than a power of 2 (8 – 1 = 7, 16 – 1 = 15, 32 – 1 = 31, 64 – 1 = 63, 128 – 1 = 127).
63. Series: 5, 10, 20, 40, ?
A) 75
B) 70
C) 80
D) 85
Answer: C) 80
Explanation: The series multiplies by 2 each time (5 × 2 = 10, 10 × 2 = 20, 20 × 2 = 40, 40 × 2 = 80).
64. Series: 9, 12, 16, 21, ?
A) 25
B) 26
C) 28
D) 30
Answer: B) 26
Explanation: The differences are: 3, 4, 5, so the next difference is 6. 21 + 6 = 26.
65. Series: 10, 20, 40, 80, ?
A) 100
B) 120
C) 160
D) 200
Answer: C) 160
Explanation: The series doubles each time (10 × 2 = 20, 20 × 2 = 40, 40 × 2 = 80, 80 × 2 = 160).
66. Series: 4, 8, 16, 32, ?
A) 64
B) 70
C) 72
D) 80
Answer: A) 64
Explanation: The series doubles each time (4 × 2 = 8, 8 × 2 = 16, 16 × 2 = 32, 32 × 2 = 64).
67. Series: 5, 15, 45, 135, ?
A) 385
B) 400
C) 405
D) 425
Answer: C) 405
Explanation: The series is multiplied by 3 each time (5 × 3 = 15, 15 × 3 = 45, 45 × 3 = 135, 135 × 3 = 405).
68. Series: 11, 22, 44, 88, ?
A) 132
B) 154
C) 176
D) 192
Answer: C) 176
Explanation: The series doubles each time (11 × 2 = 22, 22 × 2 = 44, 44 × 2 = 88, 88 × 2 = 176).
69. Series: 2, 6, 12, 20, 30, ?
A) 40
B) 42
C) 45
D) 48
Answer: B) 42
Explanation: The differences between terms are: 4, 6, 8, 10, so the next difference is 12. 30 + 12 = 42.
70. Series: 5, 7, 9, 11, ?
A) 12
B) 13
C) 14
D) 15
Answer: B) 13
Explanation: The series increases by 2 each time (5 + 2 = 7, 7 + 2 = 9, 9 + 2 = 11, 11 + 2 = 13).
71. Series: 1, 3, 6, 10, 15, ?
A) 20
B) 21
C) 22
D) 25
Answer: B) 21
Explanation: The differences are: 2, 3, 4, 5, so the next difference is 6. 15 + 6 = 21.
72. Series: 2, 4, 8, 16, ?
A) 32
B) 36
C) 40
D) 44
Answer: A) 32
Explanation: The series doubles each time (2 × 2 = 4, 4 × 2 = 8, 8 × 2 = 16, 16 × 2 = 32).
73. Series: 2, 3, 5, 8, 12, ?
A) 17
B) 18
C) 19
D) 20
Answer: A) 17
Explanation: The differences are: 1, 2, 3, 4, so the next difference is 5. 12 + 5 = 17.
74. Series: 9, 18, 36, 72, ?
A) 130
B) 144
C) 160
D) 180
Answer: B) 144
Explanation: The series doubles each time (9 × 2 = 18, 18 × 2 = 36, 36 × 2 = 72, 72 × 2 = 144).
75. Series: 1, 3, 7, 15, 31, ?
A) 61
B) 63
C) 64
D) 65
Answer: B) 63
Explanation: The series follows the pattern: each term is 1 less than a power of 2 (2 – 1 = 1, 4 – 1 = 3, 8 – 1 = 7, 16 – 1 = 15, 32 – 1 = 31, 64 – 1 = 63).
76. Series: 7, 13, 19, 25, ?
A) 31
B) 33
C) 35
D) 37
Answer: A) 31
Explanation: The series increases by 6 each time (7 + 6 = 13, 13 + 6 = 19, 19 + 6 = 25, 25 + 6 = 31).
77. Series: 1, 3, 9, 27, ?
A) 72
B) 81
C) 90
D) 120
Answer: B) 81
Explanation: The series multiplies by 3 each time (1 × 3 = 3, 3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81).
78. Series: 3, 6, 12, 24, ?
A) 48
B) 60
C) 72
D) 96
Answer: A) 48
Explanation: The series doubles each time (3 × 2 = 6, 6 × 2 = 12, 12 × 2 = 24, 24 × 2 = 48).
79. Series: 1, 2, 4, 8, ?
A) 10
B) 12
C) 16
D) 20
Answer: C) 16
Explanation: The series doubles each time (1 × 2 = 2, 2 × 2 = 4, 4 × 2 = 8, 8 × 2 = 16).
80. Series: 1, 3, 9, 27, ?
A) 81
B) 85
C) 90
D) 100
Answer: A) 81
Explanation: The series multiplies by 3 each time (1 × 3 = 3, 3 × 3 = 9, 9 × 3 = 27, 27 × 3 = 81).
These 80 challenging number series questions are great for sharpening your logical reasoning and pattern recognition skills, crucial for high-level exams. Practice regularly, and you’ll improve your speed and accuracy significantly!
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