Quantitative Aptitude
Quantitative Aptitude in the IBPS SO prelims (50 questions for most posts) tests numerical fluency and interpretation: arithmetic word problems, data interpretation (tabular, bar, pie, line and caselet), number series, quadratic equations, simplification/approximation, and basic probability and combinations.
Core rules
- Memorise fraction-percentage equivalents: 1/8 = 12.5%, 1/16 = 6.25%, 1/6 = 16.66%. They turn many DI calculations into mental arithmetic.
- In data interpretation, note the units and the base of each percentage. Compute only the requested value; use approximation when options are far apart.
- For number series, test differences, ratios, squares/cubes and alternating patterns before assuming a single rule.
- In quadratic comparisons, factorise both equations, then compare roots; do not assume x > y from the sign of the constant.
- For arithmetic, write the equation from the question before calculating; avoid chaining several steps mentally.
Worked example
A shopkeeper marks an article 40% above cost and gives a 25% discount. Find the profit percentage. Let cost price = 100. Marked price = 140. Selling price = 140 × (1 − 0.25) = 105. Profit = 105 − 100 = 5, so profit = 5%. Shortcut: successive change = +40% and −25% gives 40 − 25 − (40×25/100) = 5%.
Traps
- Taking a discount percentage on cost price instead of marked price.
- Mixing km/h and m/s; multiply by 5/18 to convert km/h to m/s.
- In DI, using the total when the question asks for a segment, or ignoring "approximately".
- Negative marking: one-fourth of the marks is deducted for a wrong answer.