Mathematics (Arithmetic and Basic Numerical Ability)
Mathematics tests arithmetic and basic numerical ability: percentages, ratio, average, profit and loss, interest, time–speed–distance, and LCM/HCF. Show the formula, substitute, then check units.
Core formulas
- Percentage change = (change/original) × 100.
- Profit % = (SP − CP)/CP × 100; loss % also uses CP as the base.
- Simple interest = P × R × T/100; compound amount = P(1 + R/100)^T.
- Average = sum/number; speed = distance/time.
- LCM × HCF = product of two numbers.
Worked example
Question: “An article bought for ₹800 is sold for ₹920. Find the profit percentage.” Profit = 920 − 800 = ₹120. Profit % = 120/800 × 100 = 15%. The base is the cost price, not the selling price.
Traps
- Using SP as the denominator for profit percentage.
- Adding successive percentage changes directly; 20% then 10% is not 30%.
- Forgetting to convert minutes to hours in speed questions.
- Mixing simple and compound interest for more than one year.
- Ignoring that LCM × HCF applies to two numbers, not three.