Number Series Questions and Answers for Competitive Exams

Number Series Questions and Answers for Competitive Exams

Number Series – Complete Notes for Competitive Exams

Introduction

Number Series is an important topic in the Quantitative & Reasoning Ability sections of competitive exams like SSC, Banking, Railway, and Defence.

Questions test a candidate’s ability to:

  • Identify patterns in sequences
  • Apply arithmetic or logical reasoning
  • Predict the next term(s) in a series

Types of Number Series Questions

1. Simple Arithmetic Series

  • Numbers increase or decrease by a fixed value.
    Example: 2, 4, 6, 8, ? → 10

2. Geometric Series

  • Each term is multiplied or divided by a fixed number.
    Example: 2, 4, 8, 16, ? → 32

3. Square / Cube Series

  • Terms are squares or cubes of natural numbers.
    Example: 1, 4, 9, 16, ? → 25

4. Mixed Series

  • Combination of addition, subtraction, multiplication, or division.
    Example: 2, 4, 8, 14, 22, ? → 32

5. Alternate Series

  • Two or more patterns alternate in the sequence.
    Example: 2, 5, 4, 7, 6, 9, ? → 8

6. Complex Patterns

  • Series may involve squares, cubes, prime numbers, or factorials.
    Example: 2, 3, 5, 10, 17, 26, ? → 37

Short Tricks to Solve Number Series

  • 🔢 Identify differences between terms
  • ✨ Check for square, cube, or factorial patterns
  • ➕ Use addition/subtraction patterns
  • ✖️ Use multiplication/division patterns
  • 🔄 Look for alternating or repeating sequences
  • ⏱ Practice to increase speed and accuracy

Common Mistakes to Avoid

  • Jumping to conclusions without checking the pattern
  • Ignoring alternate sequences
  • Forgetting complex arithmetic or geometric patterns
  • Skipping step-by-step verification

Example Question

Series: 2, 6, 12, 20, ?
Solution: Differences: 4, 6, 8 → Next difference = 10 → Next term = 20 + 10 = 30

Number Series Questions

Q1. 2, 4, 6, 8, ?

Q2. 3, 6, 12, 24, ?

Q3. 1, 4, 9, 16, ?

Q4. 5, 10, 20, 40, ?

Q5. 2, 5, 10, 17, 26, ?

Q6. 1, 1, 2, 6, 24, ?

Q7. 7, 14, 28, 56, ?

Q8. 3, 9, 27, 81, ?

Q9. 2, 6, 12, 20, ?

Q10. 5, 10, 15, 20, ?

Q11. 11, 21, 31, 41, ?

Q12. 1, 2, 6, 24, 120, ?

Q13. 13, 26, 39, 52, ?

Q14. 2, 3, 5, 8, 12, ?

Q15. 1, 8, 27, 64, ?

Q16. 4, 7, 11, 18, ?

Q17. 6, 11, 21, 36, ?

Q18. 2, 4, 8, 32, ?

Q19. 5, 15, 45, 135, ?

Q20. 10, 20, 40, 80, ?

Q21. 3, 5, 9, 17, 33, ?

Q22. 1, 3, 9, 27, 81, ?

Q23. 7, 14, 28, 56, 112, ?

Q24. 2, 6, 12, 20, 30, ?

Q25. 1, 2, 4, 8, 16, ?

Answer

Answers

Q1. 10
Q2. 48
Q3. 25
Q4. 80
Q5. 37
Q6. 120
Q7. 112
Q8. 243
Q9. 30
Q10. 25
Q11. 51
Q12. 720
Q13. 65
Q14. 17
Q15. 125
Q16. 29
Q17. 56
Q18. 128
Q19. 405
Q20. 160
Q21. 65
Q22. 243
Q23. 224
Q24. 42
Q25. 32