Quantitative Aptitude: Arithmetic, Series and Data Interpretation
Quantitative Aptitude contributes 20 questions to NABARD Grade A Phase I. The weight is on arithmetic and interpretation rather than on high-level mathematics: simplification and approximation, number series (missing and wrong term), quadratic equations, percentage, ratio and average, profit and loss, simple and compound interest, time and work, pipes and cisterns, speed-distance-trains, boats, mixtures, partnership, mensuration, elementary probability, and one or two data interpretation sets (tabular, bar, pie or caselet).
Core rules
- In simplification and approximation, round to convenient values and check the option spread; the options are built for estimation, so full calculation wastes time.
- Use the LCM unit method for work problems and the unitary method for ratio problems; both avoid fractions.
- For two years, the difference between compound and simple interest is P(r/100)². For successive percentage changes, use net = a + b + ab/100, never a + b.
- In data interpretation, read the axis, unit and base year before the first question; most errors come from reading the wrong base.
Worked example
A finishes a job in 12 days and B in 18 days. Take the LCM of 12 and 18 as 36 units of work. A does 3 units/day and B does 2 units/day; together 5 units/day. Time = 36 ÷ 5 = 7.2 days, i.e. 7⅕ days. The fraction, not "about 7 days", is what the options usually test.
Traps
- Treating successive discounts or successive percentage changes as additive.
- Confusing percentage points with per cent: a fall from 40% to 30% is 10 percentage points but a 25% decline.
- In data interpretation, computing a share of the total when the question asks for a share of one segment.
- Approximating so aggressively that two close options become indistinguishable.