Reasoning and Quantitative Aptitude
What the section tests
This domain combines logical reasoning and numerical ability in one timed paper. Reasoning items include puzzles and seating arrangements, syllogisms, blood relations, coding–decoding, input–output and data sufficiency. Quantitative items cover arithmetic such as percentage, ratio, time–work, speed and interest, plus number series, simplification, probability and data interpretation. Accuracy per question matters because negative marking punishes guesswork.
Core rules
- Syllogism: draw the minimum Venn diagram that satisfies the statements; do not add real-world assumptions. All A are B and All B are C gives All A are C.
- Puzzles: separate direct clues that fix a position from possible clues. Do not treat a possible arrangement as final.
- Data interpretation: note the unit, base year and whether the question asks for an absolute value or percentage change.
- Percentage change = (new − old) / old × 100. For successive changes, multiply factors, not add percentages.
- Compound interest: amount = P(1 + r/100)^n for annual compounding.
Worked example
A sum amounts to ₹12,100 in two years at 10% p.a. compound interest, compounded annually. Find the principal. Use 12,100 = P(1.10)^2 = 1.21P. Therefore P = 12,100 ÷ 1.21 = ₹10,000. Do not subtract two years’ simple interest of ₹2,100; compounding raises the interest because interest earns interest in year two.
Traps
- Mixing simple and compound interest formulas.
- Rounding early in DI and then choosing an option that is only close.
- In syllogism, reversing All A are B into All B are A.
- In seating puzzles, ignoring that a clue may produce two mirror-image arrangements.
- Using approximation when answer options are close together.