Logical Reasoning and Mental Ability
What is tested
Logical reasoning and mental ability covers series, analogies, coding-decoding, blood relations, direction sense, syllogism, seating arrangement, calendars and clocks, and simple non-verbal patterns. It tests structured thinking rather than memorised facts.
Core rules
- Number series: check differences, then ratios, then squares/cubes, then alternating patterns.
- Letter coding: write A=1 … Z=26 and check forward, backward and positional shifts.
- Blood relations: draw a family tree; use + for male and − for female, and horizontal lines for siblings.
- Direction sense: fix north at the top; track net displacement with a sketch.
- Syllogism: draw the minimum possible Venn diagram; a conclusion is valid only if it is true in every diagram.
- Seating: fix the most constrained person first, then place the rest.
Worked example
Find the next number: 2, 6, 12, 20, 30, ___ Reasoning: Differences are 4, 6, 8, 10-increasing by 2. The next difference is 12, so 30 + 12 = 42. 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 give 42.
Traps
- Assuming a single difference rule before checking alternating series.
- Reversing left/right after a turn in direction questions.
- Treating "some" as "all" in syllogism.
- Forgetting that in blood relations "my father's only son" may be the speaker himself.
- Off-by-one errors in calendar and clock problems.