Quantitative Aptitude
Quantitative Aptitude is the most time-critical section of NICL AO. Prelims covers simplification and approximation, number series, quadratic equations and arithmetic word problems. Mains adds data interpretation in table, bar, pie, radar and caselet form, with the same arithmetic in heavier settings: percentage, ratio, profit and loss, SI/CI, time-work, time-speed-distance, boats, pipes, mixtures and probability.
Core rules
- Percentage change: always divide by the original base; a 20% rise then a 20% fall is a net 4% fall, not zero.
- Two-year CI vs SI: the difference equals P(r/100)².
- Successive discounts: multiply, never add - 20% then 10% is 28%, not 30%.
- Work and pipes: convert everything to rate per hour; filling adds, emptying subtracts.
- DI: compute only the value the question asks for, not every cell in the table.
Worked example
Pipe A fills a tank in 12 hours; pipe B empties it in 18 hours. Both are opened together. How long does filling take?
Rates: A = 1/12 tank per hour, B = −1/18 tank per hour. Net = 1/12 − 1/18 = (3 − 2)/36 = 1/36 tank per hour. Time = 36 hours. The common wrong answer is 15 hours, obtained by averaging 12 and 18 - rates combine additively, they never average.
Traps
- Using the new value instead of the original as the percentage base.
- Reading a pie chart's angle where its share of 360° is required.
- Forcing a single difference pattern onto a number series that actually follows ×1.5 + 2 style steps.
- Fully calculating approximation questions and burning the section's time budget.
- In quadratic comparisons, forgetting to check the sign rules for negative roots.