Quantitative Aptitude and Reasoning
What is tested
Numerical ability at Class 10 level - number system, HCF/LCM, percentage, profit and loss, simple and compound interest, ratio, average, time and work, time and distance, mensuration, and simple data interpretation - plus reasoning: series, coding-decoding, analogy, blood relations, direction sense, syllogism, seating arrangement, calendar and clock.
Core rules and shortcuts
- Percentage change: successive changes multiply; a 20% rise then a 20% fall leaves 96%, i.e. a 4% net fall, not zero.
- Profit and loss: always work on cost price. Selling price from marked price = MP × (1 − discount%).
- Time and work: convert days to efficiency (A does 1/12 per day), add efficiencies, invert at the end.
- Coding-decoding: write the alphabet with positions (A=1 … Z=26); most codes are position shifts or reversals.
- Blood relations: draw a family tree and never assume gender from a name alone.
- Direction sense: draw the path on paper; the final displacement is the straight-line distance.
Worked example
A dealer marks an article 40% above cost and then allows a 25% discount. Find the profit percentage. Take cost price = 100. Marked price = 140. Selling price = 140 × 0.75 = 105. Profit = 105 − 100 = 5, so profit = 5%. The reasoning step that matters: never subtract 25 from 40 - discount applies to the marked price, not to the cost price.
Marks-losing traps
- Applying discount to cost price instead of marked price.
- Using the wrong base in percentage questions (increase on old value, decrease on new value).
- In syllogism, assuming real-world truth instead of testing the given statements only.
- Losing time on one long arrangement question instead of scanning all questions first.