Number Series

Work in this order and you will crack most series in under 30 seconds.

1. Write the differences between consecutive terms.
2. If the differences are constant → arithmetic. Done.
3. If the differences themselves form a pattern (+2, +2, +2) → second-order series. The next difference continues that pattern.
4. If the differences explode → check ratios instead (×2, ×3), or squares/cubes ±1.
5. Still stuck? Check alternate terms — two interleaved series is a favourite trick.

Never guess from the options first. The options are designed so that the off-by-one-step answer is always present.

3, 6, 11, 18, 27, ? → differences 3, 5, 7, 9 (each +2). Next difference is 11 → 27 + 11 = 38.