Quantitative Aptitude and Elementary Mathematics
What this domain tests
Quantitative Aptitude and Elementary Mathematics tests number work, percentages, ratios, averages, profit and loss, interest, time-work, speed-distance, mensuration and data interpretation. The paper rewards clean formulas and estimation.
Core rules
- Percentage change = change/original x 100. Use the base stated in the question.
- Profit% and loss% are calculated on cost price unless stated otherwise; discount is on marked price.
- Simple interest = P x R x T/100; compound interest compounds each period.
- Average = sum/count; time-work uses one-day work rates; speed = distance/time.
- Mensuration: area of rectangle = l x b; circle = pi r^2; volume of cylinder = pi r^2 h.
Worked example
A shirt marked Rs 800 is sold at 15% discount. Cost price is Rs 600. Discount = 15% of 800 = Rs 120, so selling price = Rs 680. Profit = 680 - 600 = Rs 80. Profit% = 80/600 x 100 = 13.33%. Notice that profit is on cost price, not marked price.
Traps that cost marks
Do not calculate discount on cost price; do not add simple interest and principal twice; do not mix km/h with m/s; do not use diameter in place of radius. In data interpretation, read the units and the year labels before calculating.