NDA NA 2026 — General Intelligence & Reasoning: Series Completion (20 Practice MCQs)

Practise these 20 MCQs on Series Completion for NDA NA 2026. Each question includes a detailed explanation.

Difficulty: Medium | Subject: General Intelligence & Reasoning | Topic: Series Completion

Q1. 2, 4, 8, 16, 32, ?

  • A. 64
  • B. 48
  • C. 56
  • D. 72
Answer: A — Geometric series: multiply by 2 each time. 32×2=64.

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

  • A. 36
  • B. 30
  • C. 32
  • D. 34
Answer: A — Perfect squares: 1², 2², 3², 4², 5², 6²=36.

Q3. 1, 1, 2, 3, 5, 8, ?

  • A. 13
  • B. 11
  • C. 12
  • D. 14
Answer: A — Fibonacci: 5+8=13.

Q4. 3, 9, 27, 81, ?

  • A. 243
  • B. 162
  • C. 216
  • D. 189
Answer: A — Powers of 3: 3⁵=243.

Q5. 1, 8, 27, 64, ?

  • A. 125
  • B. 100
  • C. 112
  • D. 144
Answer: A — Cubes: 5³=125.

Q6. 11, 13, 17, 19, 23, ?

  • A. 29
  • B. 27
  • C. 25
  • D. 31
Answer: A — Prime numbers in sequence. Next prime after 23 is 29.

Q7. 100, 50, 25, 12.5, ?

  • A. 6.25
  • B. 5
  • C. 8
  • D. 10
Answer: A — Each term halved: 12.5÷2=6.25.

Q8. 1, 2, 6, 24, 120, ?

  • A. 720
  • B. 600
  • C. 360
  • D. 480
Answer: A — Factorial: 6!=720.

Q9. 2, 5, 10, 17, 26, ?

  • A. 37
  • B. 35
  • C. 33
  • D. 39
Answer: A — n²+1: 6²+1=37.

Q10. 144, 121, 100, 81, ?

  • A. 64
  • B. 72
  • C. 60
  • D. 68
Answer: A — Descending perfect squares: 8²=64.

Q11. 2, 6, 12, 20, 30, ?

  • A. 42
  • B. 40
  • C. 38
  • D. 44
Answer: A — Differences: 4,6,8,10,12. Next: 30+12=42.

Q12. 6, 11, 21, 36, 56, ?

  • A. 81
  • B. 76
  • C. 91
  • D. 86
Answer: A — Differences: 5,10,15,20,25. Next: 56+25=81.

Q13. 1, 3, 7, 15, 31, ?

  • A. 63
  • B. 61
  • C. 65
  • D. 59
Answer: A — 2ⁿ-1: 2⁶-1=63.

Q14. 4, 9, 16, 25, 36, ?

  • A. 49
  • B. 42
  • C. 45
  • D. 50
Answer: A — Squares starting 2²: 7²=49.

Q15. 1, 5, 13, 29, 61, ?

  • A. 125
  • B. 121
  • C. 129
  • D. 117
Answer: A — Each term = 2×prev+3: 61×2+3=125.

Q16. 7, 14, 28, 56, ?

  • A. 112
  • B. 84
  • C. 98
  • D. 120
Answer: A — Multiply by 2: 56×2=112.

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

  • A. 13
  • B. 11
  • C. 14
  • D. 12
Answer: A — Fibonacci: 5+8=13.

Q18. 5, 10, 20, 40, ?

  • A. 80
  • B. 60
  • C. 70
  • D. 50
Answer: A — Geometric ×2: 40×2=80.

Q19. 10, 9, 8, 7, 6, ?

  • A. 5
  • B. 4
  • C. 6
  • D. 3
Answer: A — Descending by 1: 6-1=5.

Q20. 3, 6, 9, 12, 15, ?

  • A. 18
  • B. 17
  • C. 19
  • D. 16
Answer: A — Arithmetic +3: 15+3=18.

Quick Tips for Series Completion

  • Practise at least 20 questions daily.
  • Aim for under 60 seconds per question.
  • Revisit wrong answers to fix concepts.