Quantitative Aptitude and Basic Mathematics
This domain tests number sense and speed: percentages, ratio and proportion, averages, profit and loss, simple and compound interest, time-speed-distance, time and work, mensuration, LCM/HCF, and simplification.
Core formulas
- Profit% = (SP − CP)/CP × 100; Loss% uses the same base, CP.
- Discount is calculated on the marked price, not on cost price.
- SI = P × R × T/100; CI = P(1 + R/100)^T − P.
- Average = sum of values / number of values.
- Speed = distance/time; convert km/h to m/s by multiplying by 5/18.
- Work: if A finishes in x days, A's one-day work is 1/x.
- Area of a circle = πr²; volume of a cylinder = πr²h.
Worked example
A shopkeeper marks an item 25% above cost and allows a 10% discount. Find the profit percentage. Let CP = 100. MP = 125. Discount = 10% of 125 = 12.50. SP = 112.50. Profit = 12.50 on CP 100, so profit = 12.5%. Note that the 10% is taken on 125, not on 100; treating the discount as 10 on 100 gives the wrong 15%.
Traps
- Never add or subtract percentages unless the base is the same.
- In successive discounts, use 100 → after 20% → after 10%, not a flat 30%.
- In time and work, add rates, not days.
- Check units before dividing distance by time; convert minutes to hours.