Number Series and Letter Series | Definitions, Tricks & Practice MCQs with Answers” ✅

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1. What is Number Series?

👉 A number series is a sequence of numbers arranged in a specific rule or pattern.
The task is to find the missing number or identify the next number.

Example:
2, 4, 6, 8, ?
👉 Rule = +2 each time → Answer = 10

2. What is Letter Series?

👉 A letter series is a sequence of letters (like A, B, C…) arranged in a certain rule.
The task is to find the missing letter(s) or next term.

Example:
A, C, E, G, ?
👉 Rule = skipping 1 letter → Answer = I

3. Key Difference

Number Series → deals with numbers.
Letter Series → deals with letters/alphabets.

🔢 Number Series (30 MCQs)

Q1. 2, 4, 6, 8, ?
A) 9
B) 10
C) 12
D) 14
✅ Answer: B (10)
Rule: +2 each time.

Q2. 3, 6, 12, 24, ?
A) 36
B) 48
C) 50
D) 72
✅ Answer: B (48)
Rule: ×2 each time.

Q3. 5, 10, 20, 40, ?
A) 50
B) 80
C) 100
D) 200
✅ Answer: B (80)
Rule: ×2 each time.

Q4. 1, 4, 9, 16, ?
A) 20
B) 24
C) 25
D) 36
✅ Answer: C (25)
Rule: Perfect squares (1², 2², 3²…).

Q5. 2, 4, 8, 16, ?
A) 24
B) 32
C) 48
D) 64
✅ Answer: B (32)
Rule: ×2 each time.

Q6. 2, 4, 6, 8, ?

A) 9
B) 10
C) 12
D) 14
✅ Answer: B (10)
Rule: Even numbers (+2).

Q7. 5, 10, 15, 20, ?

A) 22
B) 25
C) 30
D) 35
✅ Answer: B (25)
Rule: +5 each time.

Q8. 1, 4, 9, 16, 25, ?

A) 30
B) 32
C) 36
D) 40
✅ Answer: C (36)
Rule: Perfect squares.

Q9. 2, 3, 5, 7, 11, ?

A) 12
B) 13
C) 14
D) 15
✅ Answer: B (13)
Rule: Prime numbers.

Q10. 1, 8, 27, 64, ?

A) 81
B) 100
C) 125
D) 150
✅ Answer: C (125)
Rule: Perfect cubes.

Q11. 100, 90, 80, 70, ?

A) 65
B) 60
C) 55
D) 50
✅ Answer: B (60)
Rule: –10 each time.

Q12. 3, 6, 12, 24, ?

A) 36
B) 48
C) 50
D) 60
✅ Answer: B (48)
Rule: ×2 each time.

Q13. 7, 14, 21, 28, ?

A) 30
B) 32
C) 35
D) 36
✅ Answer: C (35)
Rule: +7 each time.

Q14. 13, 26, 39, 52, ?

A) 55
B) 60
C) 65
D) 70
✅ Answer: C (65)
Rule: +13 each time.

Q15. 90, 80, 70, 60, ?

A) 50
B) 55
C) 65
D) 45
✅ Answer: A (50)
Rule: –10 each time.

Q16. 2, 4, 8, 16, 32, ?

A) 64
B) 60
C) 62
D) 65
✅ Answer: A (64)
Rule: ×2 each time.

Q17. 121, 144, 169, 196, ?

A) 200
B) 210
C) 225
D) 230
✅ Answer: C (225)
Rule: Squares (11², 12², 13², 14², 15²).

Q18. 2, 5, 10, 17, ?

A) 24
B) 25
C) 26
D) 28
✅ Answer: B (25)
Rule: +3, +5, +7, +9…

Q19. 1, 2, 6, 24, 120, ?

A) 600
B) 720
C) 840
D) 1000
✅ Answer: B (720)
Rule: Factorials (1!, 2!, 3!, 4!, 5!, 6!).

Q20. 19, 28, 37, 46, ?

A) 52
B) 55
C) 60
D) 65
✅ Answer: B (55)
Rule: +9 each time.

Q21. 3, 9, 27, 81, ?

A) 162
B) 243
C) 324
D) 400
✅ Answer: B (243)
Rule: ×3 each time.

Q22. 2, 6, 12, 20, 30, ?

A) 36
B) 40
C) 42
D) 44
✅ Answer: C (42)
Rule: Add even numbers (+4, +6, +8, +10, +12).

Q23. 7, 14, 28, 56, ?

A) 84
B) 100
C) 112
D) 120
✅ Answer: C (112)
Rule: ×2 each time.

Q24. 2, 10, 30, 68, ?

A) 100
B) 120
C) 132
D) 140
✅ Answer: C (132)
Rule: n³ + 2.

Q25. 6, 11, 21, 36, 56, ?

A) 72
B) 80
C) 81
D) 92
✅ Answer: C (81)
Rule: Add consecutive primes (+5, +10, +15, +20, +25…).

Q26. 1, 4, 13, 40, 121, ?

A) 243
B) 364
C) 400
D) 500
✅ Answer: B (364)
Rule: ×3 +1 each step.

Q27. 14, 28, 56, 112, ?

A) 212
B) 224
C) 228
D) 230
✅ Answer: B (224)
Rule: ×2 each time.

Q28. 2, 4, 12, 48, 240, ?

A) 720
B) 960
C) 1200
D) 1440
✅ Answer: B (960)
Rule: ×2, ×3, ×4, ×5, ×6.

Q29. 81, 72, 63, 54, ?

A) 46
B) 45
C) 44
D) 40
✅ Answer: B (45)
Rule: –9 each time.

Q30. 1, 2, 6, 24, 120, 720, ?

A) 1000
B) 1440
C) 5040
D) 7200
✅ Answer: C (5040)
Rule: Factorials (1!, 2!, 3!, 4!, 5!, 6!, 7!).

Q31. A, C, E, G, ?
A) I
B) H
C) J
D) K
✅ Answer: A (I)
Rule: Skipping 1 letter each time.

Q32. Z, X, V, T, ?
A) R
B) S
C) Q
D) P
✅ Answer: A (R)
Rule: –2 each time.

Q33. A, B, D, G, ?
A) J
B) K
C) L
D) M
✅ Answer: A (J)
Rule: +1, +2, +3…

Q34. B, E, H, K, ?
A) N
B) O
C) P
D) M
✅ Answer: A (N)
Rule: +3 each time.

Q35. AZ, BY, CX, DW, ?
A) EV
B) EU
C) FV
D) FU
✅ Answer: A (EV)
Rule: First letter +1, second letter –1.

Q46. A, Z, B, Y, C, X, ?
A) D
B) W
C) D and W
D) Both A and B
✅ Answer: C (D and W)
Rule: First series forward (A, B, C, D…), second backward (Z, Y, X, W…).

Q47. C, F, I, L, ?
A) O
B) P
C) Q
D) R
✅ Answer: A (O)
Rule: +3 each time.

Q48. M, N, P, Q, S, ?
A) T
B) U
C) V
D) W
✅ Answer: B (U)
Rule: Skip one, alternate +1, +2.

Q49. AA, BB, CC, DD, ?
A) EE
B) FF
C) GG
D) HH
✅ Answer: A (EE)
Rule: Repetition of same letters.

Q50. A, C, F, J, O, ?
A) U
B) V
C) W
D) X
✅ Answer: A (U)
Rule: +2, +3, +4, +5…