Reasoning, Mental Ability and Aptitude
What this domain tests
Number and letter series, analogy, coding-decoding, blood relations, direction sense, ranking and order, syllogism, linear and circular seating, puzzles, clocks and calendars, plus non-verbal items such as mirror images, embedded figures, paper folding and dice.
Core rules
- Number series: check first differences, then second differences, then ratios; alternate-term series are common.
- Letter series: write A = 1 to Z = 26 and use the EJOTY anchors (E = 5, J = 10, O = 15, T = 20, Y = 25).
- Blood relations: convert every sentence into a symbol chain (+ male, − female, = spouse) before answering; never answer mid-reading.
- Syllogism: draw Venn diagrams; 'only a few A are B' means some A are B and some A are not B.
- Circular seating: fix one person, note facing direction, then place others clockwise or anticlockwise accordingly.
- Direction sense: net displacement uses Pythagoras when turns are at right angles.
Worked example
Find the next term: 2, 6, 12, 20, 30, ? First differences: 4, 6, 8, 10 - increasing by 2 each time. The next difference is 12, so the next term is 30 + 12 = 42. Cross-check with the pattern n(n+1): 1×2=2, 2×3=6, 3×4=12, 4×5=20, 5×6=30, 6×7=42. Both routes agree, which confirms the answer.
Worked example 2 (direction)
A man walks 5 km north, turns right and walks 12 km. Displacement = √(25 + 144) = 13 km, direction north-east.
Traps that cost marks
Assuming everyone faces the centre in circular arrangements. Ignoring the 'either-or' possibility in syllogism when two conclusions are individually doubtful but jointly exhaustive. In ranking questions, subtracting one where the person is counted twice. In mirror image items, mirroring the whole figure instead of the correct axis.