Mental Ability and Reasoning
Mental Ability and Reasoning tests speed and pattern recognition rather than mathematics: number series, coding–decoding, blood relations, direction sense, syllogism, seating arrangements, clocks, calendars, dice, ranking and alphanumeric puzzles. The section rewards a candidate who writes a small diagram instead of holding conditions in memory, because most wrong answers come from a dropped constraint rather than a missed trick.
Rules worth memorising
- Number series: test differences, then second differences, then ratios, squares or cubes with a constant, alternating sub-series, and primes before guessing.
- Coding: convert letters to positions (A=1 to Z=26) and use reverse values (A=26) when shifts are negative.
- Blood relations: draw a family tree with + for male and − for female; never solve verbally.
- Syllogism: draw the minimum Venn diagram. Some A are B reverses to some B are A; all A are B does not.
- Direction: count turns, then use Pythagoras for net displacement.
- Calendar: odd days - ordinary year 1, leap year 2; 100 years 5, 200 years 3, 300 years 1, 400 years 0. Century years are leap only if divisible by 400.
- Clock: minute hand 6° per minute, hour hand 0.5°; hands coincide 22 times a day, not 24.
Worked example
Series: 2, 6, 12, 20, 30, ? Differences are 4, 6, 8, 10 - rising by 2, so the next difference is 12 and the answer is 42. Cross-check with n(n+1): 1×2, 2×3, 3×4, 4×5, 5×6, 6×7 = 42. Two independent routes agreeing is the confirmation signal. Calendar check: if 1 January 2024 was a Monday, then 1 January 2025 was a Wednesday, because 2024 is a leap year with 366 days = 52 weeks + 2 odd days.
Traps
- Reading some as only some in syllogism, or forcing an either–or answer when only one conclusion follows.
- Forgetting the facing direction of persons in seating puzzles.
- Treating 1900 or 1800 as leap years; only 1600 and 2000 qualify.