Reasoning and Mental Ability
Reasoning and Mental Ability
This domain tests pattern recognition, logical deduction and spatial thinking under time pressure. Typical items are number series, coding-decoding, blood relations, direction sense, syllogism, analogy and seating or ranking puzzles.
Core rules
- Number series: find the operation between consecutive terms. Check differences first, then ratios, then alternating or combined patterns. Do not force a pattern after one match.
- Coding-decoding: write the alphabet with positions A=1 to Z=26. Check whether letters are shifted, reversed, or replaced by their opposite letter (A with Z, B with Y).
- Blood relations: draw a family tree with separate branches for male and female; use plus and minus signs consistently. Brother of my father is uncle; son of my sister is nephew.
- Direction sense: fix north at the top. A right turn from north is east; a left turn from north is west. Net displacement uses the Pythagorean theorem when the path is at right angles.
- Syllogism: use Venn diagrams. A conclusion is valid only if it follows in every possible diagram consistent with the statements.
Worked example
Series: 2, 6, 12, 20, 30, ?. Differences: 4, 6, 8, 10. The differences increase by 2, so the next difference is 12 and the next term is 30 + 12 = 42. The terms also fit n(n+1): 1×2, 2×3, 3×4, 4×5, 5×6, so the next is 6×7 = 42. Two independent checks support the answer.
Traps
Do not stop at the first plausible pattern; test it on at least two steps. Do not reverse left and right when a person is facing south. In blood relations, do not assume gender from a name or role unless stated. In syllogism, do not use real-world knowledge that the statements do not give.