Quantitative Aptitude and Reasoning
Quantitative Aptitude and Reasoning tests numerical speed and logical structure: percentages, ratio and proportion, averages, profit and loss, interest, time–work, speed–distance, mensuration, series, coding–decoding, blood relations, syllogism and seating arrangement. PDO papers reward clean method over lengthy calculation.
Core rules
- Percentage change = (change ÷ original) × 100.
- Profit% = (profit ÷ cost price) × 100; discount is always calculated on marked price.
- Simple interest = P × R × T ÷ 100; compound interest compounds each period.
- Work: if A finishes in x days, A’s one-day work is 1/x; combine rates for joint work.
- Speed = distance ÷ time; convert km/h to m/s by multiplying by 5/18.
- In syllogism, draw minimal overlapping sets and accept only conclusions that must follow.
Worked example
A shopkeeper marks an article 25% above cost and allows a 10% discount. Let cost price = ₹100. Marked price = ₹125. Selling price = 125 × 0.90 = ₹112.50. Profit = ₹12.50, so profit% = 12.50/100 × 100 = 12.5%. Do not subtract 10% from 25% and answer 15%; the discount applies to the marked price, not the cost price.
Traps
Percentage points and percent change are different. A 20% increase followed by a 20% decrease does not return to the original value; it gives 96%. In time–work, add rates, not days. In reasoning, do not import real-world assumptions into syllogisms; follow the premises strictly.