Number Series — The Six Patterns Behind Almost Every Question

Why Number Series Is Free Marks

Every reasoning section opens with a number series, and papers reuse the same handful of patterns year after year. There is nothing to memorise here — only a fixed procedure to run.

The procedure, in order:

1. 1.Write the difference row under the series: subtract each term from the next.
2. 2.If the differences are equal → arithmetic series. Done.
3. 3.If the differences themselves form a pattern → take the difference of the differences.
4. 4.If the differences grow fast, test ratios instead: divide each term by the one before it.
5. 5.Still nothing? Test squares, cubes and prime numbers against the terms.
6. 6.Last resort: split the series into alternate terms — odd positions and even positions read as two separate series.

Ninety per cent of questions surrender at step 2 or step 4. Never stare at a series; write the difference row. The pattern is almost always visible on paper and almost never visible in your head.

1. Find the next term: 5, 11, 23, 47, ?

2. Find the next term: 3, 8, 15, 24, 35, ?

3. Which term is wrong in the series 4, 9, 19, 39, 79, 160?

4. Find the next term: 1, 4, 27, 256, ?

5. Find the next term: 2, 3, 5, 7, 11, 13, ?

6. Find the next term: 6, 12, 21, 33, ?

7. Find the next term: 3, 7, 6, 14, 12, 28, 24, ?

8. Find the next term: 121, 144, 169, 196, ?