Quantitative Techniques: Clean Setup and Percentage Bases
What Quantitative Techniques tests
CLAT quantitative techniques are short, data-led problems: percentages, ratios, averages, profit and loss, simple and compound interest, time-speed-distance, time-work, basic probability and combinations, and interpretation of tables or charts. Calculator use is not allowed, so estimation and clean setup matter.
Core rules
- Identify the base for every percentage. A discount is usually on marked price, not cost.
- Convert ratios to a common unit before combining.
- Average speed is total distance divided by total time, not the mean of speeds.
- For successive percentage changes, multiply factors: +20% then -10% gives 1.2 × 0.9 = 1.08.
- In data interpretation, read units and the exact comparison before calculating.
Worked example
A shopkeeper marks an item 25% above cost and gives a 10% discount on the marked price. What is the profit percentage? Take cost = 100. Marked price = 125. Discount = 10% of 125 = 12.50. Selling price = 112.50. Profit = 12.50 on cost 100, so profit = 12.5%. The trap is taking 10% of 100 and reporting 15%; the discount applies to the marked price.
Traps
Do not average percentages. Check whether interest is simple or compounded and the compounding period. Convert minutes to hours in speed problems. In probability, confirm whether draws are with or without replacement. Approximate only when options are far apart.