Quantitative Techniques: Pattern Recognition Under Time Pressure
AILET's Quantitative Techniques section is short but not free marks. It tests Class 8–10 arithmetic under time pressure, and one arithmetic slip cancels the gain. Speed comes from recognising standard patterns, not from calculating faster.
Topics that recur
- Percentages, profit and loss, successive discounts
- Ratio, proportion, averages, mixtures and alligation
- Time–speed–distance, trains, boats and streams
- Time and work, pipes and cisterns
- Simple and compound interest
- Permutations, combinations, basic probability
- Mensuration and data interpretation
Worked example
A trader marks an item 40% above cost and then allows a 25% discount. Find his profit percentage. Let CP = 100. Then MP = 140. The 25% discount is taken on the marked price, so SP = 140 × 0.75 = 105. Profit = 105 − 100 = 5, giving 5%.
Shortcuts worth drilling
- Successive percentage change: a% then b% gives a + b + ab/100.
- Time and work: convert days into units of work per day, then add rates.
- Two-year compound interest: CI = P[(1 + r/100)² − 1].
Traps that cost marks
- Applying the discount to cost price instead of marked price.
- Using the wrong base for a percentage change.
- Treating simple interest as compound interest, or vice versa.
- Rounding too early in data-interpretation questions.