Quantitative Aptitude: Arithmetic and Data Interpretation for AEEE
Quantitative Aptitude checks numerical reasoning under time pressure: number systems, percentages, profit and loss, ratio and proportion, averages, simple and compound interest, time–speed–distance, time and work, permutations and combinations, probability, mensuration and data interpretation. The mathematics is school-level; speed and error control decide the score.
Core rules
- Percentage change = (change/original) × 100. A rise from 40 to 50 is a 25% increase, not 10%.
- Successive changes of a% and b% give a net change of a + b + ab/100 percent.
- For equal distances at speeds u and v, average speed = 2uv/(u + v), not (u + v)/2.
- Work rates add: if A finishes in a days and B in b days, together they take ab/(a + b) days.
- Compound interest: A = P(1 + r/100)ⁿ; simple interest: SI = Prt/100.
Worked example
A can finish a job in 12 days and B in 18 days. Working together, how long will they take? Rates: A = 1/12 of the job per day, B = 1/18 per day. Combined rate = 1/12 + 1/18 = 3/36 + 2/36 = 5/36 per day. Time = 36/5 = 7.2 days, that is, 7 days and 4.8 hours. Shortcut: ab/(a + b) = (12 × 18)/30 = 216/30 = 7.2 days. The shortcut works only for two workers; for three, use the rate method.
Traps that cost marks
- Adding successive discounts directly: 20% then 10% is a 28% net discount, not 30%.
- Charging profit percentage on the selling price instead of the cost price.
- Mixing percentage points with percent change.
- In data interpretation, reading a table row against the wrong year or the wrong unit (lakh vs crore).
- Rounding intermediate values; carry fractions until the final step.