Numerical Reasoning and Quantitative Aptitude
Numerical Reasoning and Quantitative Aptitude
This domain tests arithmetic fluency and the ability to translate short workplace-style word problems into calculations. Expect percentages, ratios, averages, rates, simple and compound interest, and number sequences, usually with distractors and time pressure.
Core rules
- Percentage change uses the original value as denominator: change ÷ original × 100.
- Successive percentage changes multiply factors, not add percentages: +25% then −10% is 1.25 × 0.90 = 1.125.
- Ratios scale only when every part is multiplied by the same number; convert to a common unit first.
- Average = total ÷ count; if averages of groups are combined, weight by group size.
- Work rate adds in units per hour: combined rate = 1/a + 1/b.
Worked example
A trader buys goods for 2,400, marks them up by 25%, then gives a 10% discount. Selling price = 2,400 × 1.25 × 0.90 = 2,700. Profit = 2,700 − 2,400 = 300. Profit percentage = 300 ÷ 2,400 × 100 = 12.5%, not 15%. The discount applies to the marked price, and profit percentage applies to cost.
Traps
- Applying a discount to cost instead of marked price.
- Adding successive percentages.
- Mixing units such as minutes and hours.
- Choosing the wrong base for a percentage comparison.
- Rounding too early in multi-step items.