General Mathematics and Quantitative Aptitude: Arithmetic with Speed
General Mathematics and Quantitative Aptitude tests numerical reasoning through percentage, ratio and proportion, average, profit and loss, simple and compound interest, time and work, speed and distance, mensuration, simplification and number system. The paper rewards clean method and approximation, not lengthy algebra.
Core formulas
- Percentage change = (change ÷ original) × 100.
- Successive discounts are not added: use SP = MP × (1 − d1) × (1 − d2).
- Average = sum ÷ number of items; if every item increases by k, the average increases by k.
- Work: if A alone takes a days and B alone takes b days, together they take ab/(a+b) days.
- Speed = distance ÷ time; convert km/h to m/s by multiplying by 5/18.
- Simple interest = P × R × T ÷ 100.
Worked example
A shopkeeper marks an article 40% above cost price and then gives a 25% discount. Find the profit percentage. Let CP = 100. Marked price = 140. Selling price = 140 × 0.75 = 105. Profit = 105 − 100 = 5, so profit is 5% on cost. The tempting error is to subtract 25% from 40% and claim 15% profit; discounts apply to the marked price, not to the cost price.
Traps that cost marks
Distinguish percentage points from percent change. Read whether profit is on cost or selling price. Keep units consistent in speed and mensuration questions. In time-and-work, do not add days directly; add rates. In compound interest, use the number of compounding periods, not merely the annual rate.
Practice target
Learn tables to 20, squares to 30 and common fractions; they shorten simplification questions.