Mental Ability and Reasoning
What is tested
This section rewards pattern recognition under time pressure: number and letter series, coding–decoding, blood relations, direction sense, syllogism, analogy, classification and seating arrangement.
Core approaches
- Series: check differences first, then ratios, then squares and cubes; alternate series interleave two patterns.
- Coding: convert letters to positions (A = 1 … Z = 26) and compare shifts; the shift may be +1, +2, +3 or reversed for alternate letters.
- Blood relations: draw a small family tree; use '+' and '−' marks for male and female, and never assume gender from a name or role.
- Direction: sketch the path on paper; net displacement is the straight line from start to finish, not the sum of steps.
- Syllogism: test the conclusion in every possible Venn diagram; a conclusion is valid only if it holds in all of them.
Worked example
Find the next term: 2, 6, 12, 20, 30, ?. Differences are 4, 6, 8, 10 - increasing by 2, so the next difference is 12 and the answer is 42. Equivalently, the terms are n(n + 1) for n = 1, 2, 3 …, giving 6 × 7 = 42.
Traps
Assuming a pattern from a single difference without verifying it twice; treating 'some A are B' as reversible (it is, but 'all A are B' is not); forgetting that a person facing south has east on the left; over-writing rough work instead of using a clean diagram.