RRB CMA General Intelligence & Reasoning: Number Series Practice Questions

These 20 MCQs are designed for RRB CMA 2026. Study the explanations carefully to master Number Series.

Q1. 2, 6, 12, 20, 30, ?

  • A) 42
  • B) 40
  • C) 44
  • D) 36

Answer: A — Differences: 4,6,8,10,12 → next term = 30+12=42.

Q2. 1, 4, 9, 16, 25, ?

  • A) 36
  • B) 34
  • C) 38
  • D) 30

Answer: A — Perfect squares: 1²,2²,3²,4²,5² → 6²=36.

Q3. 3, 8, 15, 24, 35, ?

  • A) 48
  • B) 50
  • C) 46
  • D) 52

Answer: A — Differences: 5,7,9,11,13 → 35+13=48.

Q4. 5, 10, 20, 40, 80, ?

  • A) 160
  • B) 140
  • C) 120
  • D) 200

Answer: A — Each term ×2: 80×2=160.

Q5. 1, 3, 7, 15, 31, ?

  • A) 63
  • B) 61
  • C) 59
  • D) 65

Answer: A — Each term ×2+1: 31×2+1=63.

Q6. 100, 96, 88, 76, 60, ?

  • A) 40
  • B) 42
  • C) 44
  • D) 38

Answer: A — Differences: –4,–8,–12,–16,–20 → 60–20=40.

Q7. 2, 3, 5, 8, 13, 21, ?

  • A) 34
  • B) 32
  • C) 36
  • D) 30

Answer: A — Fibonacci sequence: each term = sum of two preceding → 13+21=34.

Q8. 7, 14, 28, 56, ?

  • A) 112
  • B) 100
  • C) 108
  • D) 120

Answer: A — ×2 each time: 56×2=112.

Q9. 1, 8, 27, 64, 125, ?

  • A) 216
  • B) 196
  • C) 256
  • D) 169

Answer: A — Cubes: 1³,2³,3³,4³,5³ → 6³=216.

Q10. 144, 121, 100, 81, 64, ?

  • A) 49
  • B) 50
  • C) 48
  • D) 36

Answer: A — Perfect squares descending: 12²,11²,10²,9²,8² → 7²=49.

Q11. 3, 9, 27, 81, ?

  • A) 243
  • B) 162
  • C) 324
  • D) 200

Answer: A — ×3 each time: 81×3=243.

Q12. 10, 14, 19, 25, 32, ?

  • A) 40
  • B) 39
  • C) 41
  • D) 38

Answer: A — Differences: 4,5,6,7,8 → 32+8=40.

Q13. 256, 64, 16, 4, ?

  • A) 1
  • B) 2
  • C) 0.5
  • D) 0.25

Answer: A — ÷4 each time: 4÷4=1.

Q14. 1, 2, 6, 24, 120, ?

  • A) 720
  • B) 600
  • C) 840
  • D) 480

Answer: A — Factorials: 1!,2!,3!,4!,5! → 6!=720.

Q15. 2, 5, 11, 23, 47, ?

  • A) 95
  • B) 91
  • C) 93
  • D) 99

Answer: A — Each term ×2+1: 47×2+1=95.

Q16. 17, 13, 9, 5, ?

  • A) 1
  • B) 3
  • C) 2
  • D) 0

Answer: A — –4 each time: 5–4=1.

Q17. 0, 1, 1, 2, 3, 5, 8, ?

  • A) 13
  • B) 11
  • C) 12
  • D) 14

Answer: A — Fibonacci: 5+8=13.

Q18. 4, 9, 25, 49, 121, ?

  • A) 169
  • B) 144
  • C) 196
  • D) 225

Answer: A — Squares of primes: 2²,3²,5²,7²,11² → 13²=169.

Q19. 50, 45, 35, 20, ?

  • A) 0
  • B) 5
  • C) 10
  • D) –5

Answer: A — Differences: –5,–10,–15,–20 → 20–20=0.

Q20. 6, 11, 21, 41, 81, ?

  • A) 161
  • B) 151
  • C) 141
  • D) 171

Answer: A — Each term ×2–1: 81×2–1=161.