Quantitative Aptitude and Mathematics
What is tested
Quantitative aptitude checks arithmetic speed and accuracy: percentage, ratio and proportion, average, profit and loss, simple and compound interest, time-work, speed-distance, mensuration and number series. The maths is school-level; the challenge is choosing the fastest method under time pressure.
Core rules
- Percentage change is always calculated on the base given, not on the final value.
- Profit/loss is on cost price unless stated otherwise; discount is on marked price.
- Average = sum ÷ number; for consecutive numbers the average is the middle term.
- Simple interest: SI = P×R×T/100. Compound interest compounds each period.
- Time-work: work rate = 1/time; combined rate adds.
- Speed = distance/time; convert km/h to m/s by multiplying by 5/18.
Worked example
A shopkeeper marks an item 40% above cost and then gives a 25% discount. Find the profit percentage. Reasoning: Let CP = 100. Marked price = 100 + 40% of 100 = 140. Selling price = 140 − 25% of 140 = 140 − 35 = 105. Profit = 105 − 100 = 5. Profit % = 5/100 × 100 = 5%. Do not subtract 40 − 25 = 15; the discount is on a larger base.
Traps
- Applying percentage to the wrong base.
- Mixing SI and CI for multi-year periods.
- Forgetting unit conversion (km/h vs m/s, minutes vs hours).
- Treating "more than" and "less than" as reversible: 20% more than 100 is 120, but 20% less than 120 is 96, not 100.
- Ignoring that average speed for equal distances is the harmonic mean, not the arithmetic mean.