Quantitative Aptitude / Numerical Ability
Quantitative Aptitude / Numerical Ability
The paper mixes speed arithmetic with standard school mathematics: simplification and approximation, number series, quadratic comparison, data interpretation (table, bar, pie, line) and word problems on percentage, ratio, average, profit and loss, simple and compound interest, time-work, speed-distance, boats and pipes.
What to lock down
- Percentage base: always ask "percentage of what?" A 20% rise followed by a 20% fall leaves 96% of the original, not 100%.
- CI versus SI: CI = P(1 + r/100)^n. For two years, CI − SI = P(r/100)².
- Time and work: convert everything to rates. If A finishes in 12 days and B in 18, together they complete 1/12 + 1/18 = 5/36 per day, i.e. 36/5 = 7.2 days.
- Data interpretation: read the units and the year row before computing; answer in the unit asked.
Worked example
A sum doubles in 8 years at simple interest. Find the rate. Interest earned equals the principal, so P = P × r × 8 / 100, giving r = 100/8 = 12.5% per annum. Note the limit of the shortcut: under compound interest, doubling happens sooner, so this equation cannot be reused there.
Traps that cost marks
In approximation questions with close options, round only one step and keep the rest exact. Convert minutes to hours before using speed formulas. Never apply the SI formula to a CI question. In pie-chart DI, check whether a question asks for a share of the total or a percentage change between two years - the arithmetic is different.