Quantitative Aptitude and Reasoning: Shortcuts, Patterns and Accuracy
What the paper tests
Quantitative Aptitude and Reasoning tests speed and accuracy in school arithmetic plus verbal and non-verbal reasoning: series, analogy, coding–decoding, blood relations, direction sense, syllogism, clocks, calendars and figures. Most items are solvable in under a minute if the pattern is identified first.
Core rules
- Percentage: always on a base; successive changes multiply, they do not add. A 20% rise then 20% fall gives 96%, not 100%.
- Profit and loss: profit% = (SP − CP)/CP × 100; discount is on the marked price, not the cost.
- Average: sum ÷ count; for equal distances at speeds a and b, average speed is 2ab/(a+b), not (a+b)/2.
- Ratio: convert to a common unit before forming the ratio; each share = ratio part × total.
- Time and work: use rates; if A does a job in 12 days and B in 18, together they do 1/12 + 1/18 = 5/36 per day, so 36/5 = 7.2 days.
- Reasoning: in direction questions, draw the path and turn relative to the facing direction; in syllogism, test every possible diagram, not just the obvious one.
Worked example
A shopkeeper marks an item 40% above cost and gives a 25% discount. Take CP = ₹100. Marked price = ₹140. Selling price = 140 × 0.75 = ₹105. Profit = ₹5, so profit% = 5%. The discount percentage and the mark-up percentage act on different bases, which is why they do not cancel.
Traps
Applying profit% to SP; averaging speeds without weighting distance; inferring “all B are A” from “all A are B”; miscounting left/right after a turn; calculating clock angle as 30h without the minute-hand correction (30h − 5.5m).