Quantitative Aptitude / Numerical Ability
Quantitative Aptitude / Numerical Ability checks arithmetic fluency and interpretation, not advanced mathematics. The paper typically includes simplification and approximation, number series, percentage, ratio and proportion, average, profit and loss, simple and compound interest, time-work, speed-distance, mixtures, and data interpretation based on tables, bar graphs or pie charts.
Core rules
- Follow BODMAS and convert percentages to multipliers: a 20% rise is ×1.20; a 20% fall is ×0.80.
- In ratio problems, assign one unit and scale only at the end.
- For time-work, take total work as the LCM of individual times; add rates when people work together.
- In data interpretation, read units, base year and whether the question asks for absolute value or percentage change.
Worked example
Two clerks can digitise 600 records. A alone takes 12 days, B alone 18 days. How long together? Take total work = LCM(12,18) = 36 units. A's rate = 36/12 = 3 units/day; B's rate = 36/18 = 2 units/day. Combined rate = 5 units/day, so time = 36/5 = 7.2 days. Check: 600/12 = 50 records/day and 600/18 ≈ 33.33, giving 600/83.33 = 7.2 days.
Traps
Using the old value as the base for percentage change; adding times instead of rates in work problems; treating SI as CI for multi-year sums; ignoring "approximately" in simplification; and misreading a DI table's total row as a category. Keep units consistent before calculating.