Example 1 · level 1
Find the next term: 5, 10, 20, 40, 80, ?
Show solution
- Multiply by 2 each time.
- Next term = 160.
Answer: 160
CA FOUNDATION: QUANTITATIVE APTITUDE · LOGICAL REASONING
Logical reasoning: number series
Look at differences first; if they are not constant, check second differences, ratios, squares/cubes or two alternating series.
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Worked examples
Example 2 · level 2
Find the next term: 17, 26, 37, 50, 65, ?
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- Each term is n² + 1 for n = 4, 5, …
- Next term = 82.
Answer: 82
Example 3 · level 3
Find the next term: 4, 11, 32, 95, 284, ?
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- Each term = previous × 3 − 1.
- Next term = 851.
Answer: 851