Mathematics / Quantitative Aptitude
Quantitative aptitude here is arithmetic-heavy: percentage, ratio, average, profit and loss, simple and compound interest, time–work, time–speed–distance, mensuration and data interpretation. Speed with fractions and multiplication tables matters far more than advanced algebra.
Rules that cover most questions
- Percentage change = (change ÷ original) × 100. Successive changes of a% and b% give a + b + ab/100.
- Profit percent is on cost price; discount percent is on marked price.
- Average speed over equal distances = 2xy/(x + y), not (x + y)/2.
- SI = PRT/100; CI = P(1 + R/100)^T − P.
- Work: if A finishes in x days, one day's work is 1/x; combined rates add.
- Mensuration: circle area πr², circumference 2πr; cylinder volume πr²h; sphere (4/3)πr³.
Worked example
A trader marks an article 40% above cost and allows a 25% discount. Find his profit percent. Let CP = 100, so MP = 140. The discount applies to the marked price: SP = 140 × 0.75 = 105. Profit = 105 − 100 = 5, hence 5%. Shortcut: net multiplier = 1.40 × 0.75 = 1.05.
Traps
- Applying the discount to CP, or profit percent to SP.
- Using the arithmetic mean for average speed.
- Forgetting unit conversion: km/h to m/s means multiplying by 5/18.
- Reading a monthly rate as annual in compound interest.