Quantitative Aptitude / Numerical Ability
Question mix
Quantitative Aptitude in SBI Clerk is dominated by simplification and approximation, number series (missing term and wrong term), quadratic comparison, percentage, ratio–proportion, average, profit and loss, simple and compound interest, time–work, time–speed–distance, mixtures, mensuration basics, probability, and data interpretation in tabular, bar, pie and caselet form.
Master the standard formulas and, more importantly, the shortcuts: fraction-to-percentage equivalents (1/8 = 12.5%), percentage change = (change ÷ original) × 100, successive change = a + b + ab/100, and the unitary method for ratio problems. Learn squares up to 30 and cubes up to 15 to speed up series and simplification items.
Traps: mixing units (km/h with metres, or minutes with hours); answering the wrong quantity in DI (percentage asked, absolute value given); forgetting that compound interest may be compounded half-yearly or quarterly; spending full time on 'approximate' questions that need only rounding; and series that look arithmetic but are actually squares or cubes with a constant added. Wrong-term series punish anyone who checks only the first two terms.
Worked example: two successive discounts of 20% and 10% on ₹1,000. Using a + b + ab/100 with a = −20 and b = −10 gives −20 − 10 + 2 = −28, i.e. a 28% discount, so the selling price is ₹720. Spot-check: 20% off leaves 800; 10% of 800 is 80; 800 − 80 = 720. Rule of thumb: in DI, read the legend and the unit demanded before computing; in series, test differences first, then ratios, then squares.