General Aptitude and Reasoning: Quantitative Aptitude, Mental Ability, Logical Reasoning
Core areas
Quantitative aptitude covers percentages, ratio and proportion, averages, time-speed-distance, time and work, profit and loss, simple and compound interest, mensuration, and elementary data interpretation. Mental ability includes series, coding-decoding, blood relations, direction sense, and seating arrangement. Logical reasoning adds syllogisms, statement-conclusion, and assumption-based questions.
Method over memory
These questions test disciplined procedure. For percentages, convert to fractions (25% = 1/4) to speed calculation. For time and work, use the unitary method with LCM of days. For series, check differences, then ratios, then squares and cubes.
Traps to watch
Common traps include unit mismatches (metres versus kilometres), percentage change versus percentage point change, and questions asking for the approximate value. In reasoning, distractors rely on reversing a relationship, such as swapping 'father of' with 'son of'. Always redraw blood-relation and direction diagrams.
Rule of thumb
Use the estimate-first rule: approximate the answer before computing exactly. If your exact answer is far from the estimate, recheck the setup rather than the arithmetic.
Worked example
A train covers 240 km in 3 hours, then 180 km in 2 hours. Average speed = total distance / total time = 420/5 = 84 km/h. A tempting wrong method averages 80 and 90 to get 85; the trap is averaging speeds instead of distances.