Numerical Reasoning and Quantitative Aptitude
The Numerical Reasoning and Quantitative Aptitude domain tests numerical sense rather than heavy calculation: percentages, ratios, averages, speed–distance–time, profit and loss, interest, number series, approximation, and simple data interpretation. A calculator is not assumed; estimation and a clean setup matter.
Core rules
- Successive percentage changes multiply: a 20% rise then a 10% fall is 1.20 × 0.90 = 1.08, not +10%.
- Ratio: keep units aligned; scale both parts by the same factor.
- Average: total ÷ count; for average speed with equal distances, use total distance ÷ total time, not the mean of speeds.
- Profit/loss: state the base. A 25% profit on cost is not a 25% margin on selling price.
- Series: test differences, ratios, squares/cubes and alternating patterns before guessing.
Worked example
A Rs. 2,500 item gets 20% off, then 10% off the reduced price. After 20%: 2500 × 0.80 = 2000. After 10%: 2000 × 0.90 = 1800. Total discount is Rs. 700, or 28%. A single 30% discount would give Rs. 1,750, so the two offers are not equivalent.
Traps
- Adding successive percentages (20% + 10% = 30%) instead of multiplying.
- Mixing metres and kilometres, minutes and hours.
- Rounding before the final step.
- Reading a data chart’s axis labels or units incorrectly.
- Confusing “profit on cost” with “profit on selling price.”