A checklist to run through
- Constant difference (add or subtract the same number)
- Constant ratio (multiply or divide)
- Differences that themselves form a pattern
- Squares, cubes or primes
- Two interleaved series
Worked examples
Example 1. 3, 6, 12, 24, ? Each term doubles, so the next is 48.
Example 2. 2, 5, 10, 17, 26, ? The differences are 3, 5, 7, 9, so the next difference is 11 and the answer is 37.
Speed
Check the differences first, then the ratios. If neither works, test squares and cubes. Related reasoning topics are coding-decoding and syllogisms; see how series appear in banking reasoning.
