Study Guides/Maths/Number Series Questions
Study Guide · Maths

Number Series Questions — Patterns and Types

Number series questions test pattern recognition — a critical skill for school maths, competitive exams (SSC, Railways, Banking), and IQ tests.

Question (Click to Flip)

What is the next number: 5, 10, 20, 40, ?

Answer

Each term is doubled (×2). Next term = 40 × 2 = 80. (Geometric series with ratio 2)

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Key Facts

Number series questions are compulsory in SSC CGL, IBPS PO, Railway NTPC, and most state PSC aptitude sections. Regular practice is essential.

Types of Number Series

1. Arithmetic Series (constant difference): Example: 3, 7, 11, 15, ? → Add 4 each time → Answer: 19

2. Geometric Series (constant ratio): Example: 2, 6, 18, 54, ? → Multiply by 3 → Answer: 162

3. Fibonacci-type Series (each term = sum of previous two): Example: 1, 1, 2, 3, 5, 8, ? → Answer: 13

4. Square/Cube Series: Example: 1, 4, 9, 16, 25, ? → Perfect squares (n²) → Answer: 36

5. Mixed/Alternating Series: Example: 2, 4, 3, 9, 4, 16, 5, ? → Two alternating series: (2,3,4,5) and (4,9,16,25=5²) → Answer: 25

Strategy to Solve

  1. Check if there is a constant difference between terms.
  2. If not, check for a constant ratio.
  3. Check if differences themselves form a pattern (second-level arithmetic).
  4. Look for perfect squares/cubes.
  5. Look for alternating patterns (odd/even positions).

Questions and Answers

What is the next number: 5, 10, 20, 40, ?+

Each term is doubled (×2). Next term = 40 × 2 = **80**. (Geometric series with ratio 2)

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