Quantitative Aptitude and Numerical Ability
Quantitative Aptitude and Numerical Ability checks numerical fluency, formula selection and data interpretation under time pressure. FCI AGM Phase I favours percentage, ratio, average, time-work, speed-distance, interest, profit-loss, mensuration and DI-based questions.
Core rules
- Percentage change uses a base. Successive changes multiply: net = (1 ± a)(1 ± b) − 1.
- Profit and loss are normally calculated on cost price; discount is calculated on marked price.
- Time-work: add rates for people working together; use LCM to avoid fractions.
- Simple interest = PRT/100. Compound interest = P[(1 + r/n)^(nt) − 1].
- Speed conversion: km/h to m/s multiply by 5/18; m/s to km/h multiply by 18/5.
- In DI, compute the required ratio or percentage before scanning options.
Worked example
An article costs ₹100. It is marked 25% above cost, then sold at a 12% discount. Find the profit percentage.
Marked price = 100 × 1.25 = ₹125. Selling price = 125 × 0.88 = ₹110. Profit = 110 − 100 = ₹10. Profit percentage on cost = 10/100 × 100 = 10%. The discount is on ₹125, not on ₹100; applying 12% to cost gives the wrong answer.
Traps
- Adding successive discounts instead of multiplying them.
- Calculating profit on selling price when the question says cost price.
- Using arithmetic mean for average speed when distances are equal but speeds differ; use total distance/total time.
- For half-yearly compounding, halving the annual rate but forgetting to double the periods.