Basic Mathematics and Quantitative Aptitude
Basic Mathematics and Quantitative Aptitude tests speed and accuracy in arithmetic and elementary mensuration: percentage, ratio, average, profit and loss, simple and compound interest, time-work, speed-distance, LCM/HCF and area-perimeter.
Core rules
- Profit and loss percentages are based on cost price unless the question says otherwise; discount is based on marked price.
- Percentage change uses the original value as denominator.
- Simple interest = P × R × T / 100; compound interest uses successive multiplication.
- Time-work: if A finishes in x days, one day's work is 1/x; combine rates and take the reciprocal for total time.
- For speed, keep units consistent; convert km/h to m/s by multiplying by 5/18.
Worked example
A shop marks an item at ₹800, gives a 10% discount, and still makes a 20% profit on cost. Find the cost. Discount is on marked price: SP = 800 - 80 = ₹720. Profit is on cost: SP = 1.20 × CP. So CP = 720 / 1.20 = ₹600. The reasoning is to apply each percentage to its own base; using 800 as the cost base would give a wrong answer.
Traps
Do not calculate discount on cost or profit on marked price. In successive percentage changes, do not add or subtract percentages directly. In time-work, do not average days; average rates. In mensuration, check whether the question asks for area, perimeter or volume, and keep π and unit conversions consistent.