Quantitative Aptitude and Numerical Ability
This section checks numerical ability: number system, percentage, ratio, average, profit and loss, interest, time-work, speed-distance, mensuration and data interpretation. The exam rewards formula recall plus careful unit handling.
Core rules
- Percentage change = (change / original) × 100. Profit% and loss% are calculated on cost price unless stated otherwise; discount is calculated on marked price.
- Simple interest = P × R × T / 100. Compound amount = P(1 + R/100)^T for annual compounding.
- Average = sum of values / number of values. Speed = distance / time. Work done is inversely proportional to time taken when efficiency is constant.
- Mensuration: area of rectangle = length × breadth; circle area = πr²; triangle area = ½ × base × height; volume of cuboid = l × b × h.
Worked example
A shopkeeper marks an item at ₹500, gives a 20% discount, and still makes 25% profit. Selling price = 500 × 0.80 = ₹400. Cost price = 400 / 1.25 = ₹320. Reason: discount applies to marked price, while profit percentage applies to cost price.
Traps that cost marks
Do not calculate profit on selling price when the question says cost price. In compound interest, interest is added each period. Convert minutes to hours before using speed formulas. A 20% discount followed by 20% increase is not a zero change.