Quantitative Aptitude (Basic Numeracy)
Quantitative Aptitude tests percentage, ratio, average, profit and loss, simple and compound interest, time-work, speed, and elementary algebra. The arithmetic is simple; the trap is usually the base of comparison.
Core rules
- Percentage change = (change ÷ original) × 100. Always identify the original base.
- Profit% and loss% are calculated on cost price unless stated otherwise.
- SI = P × R × T ÷ 100; CI = P(1 + R/100)^T − P.
- Average = sum ÷ number of items; total = average × number.
- Work: if A does a job in x days, A’s one-day work is 1/x.
Worked example
Question: “A shirt priced at ₹800 is sold at a 20% discount, then 10% GST is added on the discounted price. What is the final price?” Reasoning: discount = 20% of 800 = 160; discounted price = 640. GST = 10% of 640 = 64; final = 640 + 64 = ₹704. Answer: ₹704.
Traps
- Applying GST to the original price instead of the discounted price.
- Calculating profit% on selling price.
- Adding percentages directly when the bases differ.
- Forgetting to convert time units in speed problems.