Quantitative Aptitude / Mathematics
Domain overview
PERA CET's Quantitative Aptitude / Mathematics section checks numerical fluency under time pressure: arithmetic (percentage, ratio, average, profit-loss, interest, time-work, speed-distance), elementary algebra and geometry, and data interpretation from tables or text. Questions are usually single-correct and calculation-light if you choose the right base.
Core rules
- Percentage change: always divide by the original/base value, not the new value. A rise from 80 to 100 is 25%, not 20%.
- Profit and loss: use CP = 100 for markup-discount chains; successive discounts multiply, never add: 20% then 10% = 28% total discount, not 30%.
- Ratio and proportion: convert ratios to a common unit before combining; in mixtures, track the actual quantity, not just the ratio.
- Average: total = average × number of items; adding a value changes the average by the deviation divided by the new count.
- Time-speed-distance: keep units consistent; km/h to m/s multiply by 5/18.
Worked example
A shopkeeper marks an item 40% above cost and allows a 25% discount. What is the profit percentage? Let CP = 100. Marked price = 140. Selling price = 140 × (1 − 0.25) = 105. Profit = 105 − 100 = 5, so profit = 5%. The trap is adding 40% and subtracting 25% to claim 15% profit; discount applies to the marked price, not the cost price.
Traps that cost marks
Using the new value as the percentage base; adding successive discounts; mixing km/h with metres; rounding before the final step; and ignoring the word 'approximately' when options are close.