Series, Analogy & Classification
Series and analogy questions are the cheapest marks in any reasoning paper: the rules repeat, and once you can name the pattern you can solve in seconds. Almost every series is built on one of five ideas — a constant difference, a constant ratio, squares/cubes, alternating rules, or a difference-of-differences.
Don't read this page — work through it. Each block asks you to commit to an answer before it tells you anything.
Start here: what do you already know?
Series & analogy — true or false?
6 statements · 10s each
The five patterns worth memorising
| Pattern | Example | How to spot it |
|---|---|---|
| Arithmetic (constant difference) | 5, 9, 13, 17 | Differences are equal |
| Geometric (constant ratio) | 3, 6, 12, 24 | Each term divides evenly into the next |
| Square / cube | 1, 4, 9, 16 · 1, 8, 27 | Terms are familiar powers |
| Difference of differences | 2, 6, 12, 20 | First differences form their own series |
| Alternating | 2, 100, 4, 90, 8, 80 | Two interleaved rules |
Name the pattern before you solve
Sorting a series into the right family is most of the work. Do that here.
Which family does each series belong to?
0/65, 25, 125, 625
Which group does it belong to?
Commit to the next term
Move the slider to the term you think comes next, then check.
What comes next?
1/42, 6, 12, 20, 30, ?
45
Analogies: name the relation in words
An analogy is solved the moment you can say the link out loud. "Doctor is to hospital as worker is to workplace" — then apply that sentence to the options. If two options fit, your sentence was too vague; make it sharper.
Method, in order
Facts worth carrying into the hall
Exam tip: if a series looks impossible, take differences twice before you try anything clever. A constant second difference explains a large share of the "hard" series in SSC, RRB and CET papers.