Quantitative Aptitude / Data Analysis and Interpretation
Quantitative Aptitude and Data Interpretation carries 35 questions in Phase 1 and a larger weighted section in Phase 2. The paper has three layers: 10-12 arithmetic word problems (time-work, speed, mixtures, profit and loss, SI/CI, ratio, ages, probability), two or three DI sets of five questions each, and 10-15 quick items on approximation, number series and quadratic comparison.
Core rules
- Approximate before computing: options are usually spread wide, so two significant figures identify the answer and save a minute per question.
- Series: check first differences, then ratios, then second differences; an alternating jump-then-fall pattern usually signals ×n then −k.
- Quadratic comparison: x² − 7x + 12 = 0 gives roots 3 and 4; when the sum and product of roots are both positive, both roots are positive.
- DI: compute each ratio once and reuse it; percentage change = (new − old)/old × 100, with the old value as the base.
- SI = PRT/100; CI = P(1 + r)^n − P; the effective two-year compound rate is r + r + r²/100.
Worked example
A sum becomes double in 5 years at simple interest. In how many years will it become four times? Interest earned equals P in 5 years, so the rate is 20% per annum. To become four times, the interest must be 3P: 3P = P × 20 × t/100, giving t = 15 years. Note the contrast with compound interest, where doubling in 5 years would make the sum four times in exactly 10 years, not 15 - the phrase simple interest is doing the work here.
Traps
Using the new value as the denominator in percentage-change questions; forgetting to convert a per-annum rate for a months-based term; and losing an entire DI set because one intermediate figure was carried unrounded into four later questions.