Quantitative Aptitude and Numerical Ability
Quantitative Aptitude tests speed and accuracy with percentages, ratios, averages, interest, time-work, speed-distance, mensuration, and data interpretation. RVUNL JE papers usually avoid very long derivations; they reward clean conversion and the shortest correct method.
Core rules
- Percentage change = (new − old)/old × 100; successive changes multiply, they do not add.
- Profit% is calculated on cost price unless stated otherwise; discount% is calculated on marked price.
- Simple interest = P × R × T/100; compound interest = P(1 + R/100)^T − P.
- Time and work: if A does 1/a work per day and B does 1/b, together they do 1/a + 1/b per day.
- Speed = distance/time; convert km/h to m/s by multiplying by 5/18.
Worked example
A shopkeeper marks an item 40% above cost and gives a 25% discount. Take cost = 100. Marked price = 140. Discount = 25% of 140 = 35. Selling price = 105. Profit = 5 on cost 100, so profit% = 5%. The reasoning shows why the discount is applied to the marked price, not to the cost price.
Data interpretation
Read the axes and units before comparing bars. Calculate approximate values first, then eliminate options. For ratios, keep the same base; for averages, remember that the total equals average × number of items.
Traps that cost marks
Adding successive percentage changes; applying discount to cost price; mixing simple and compound interest; forgetting to convert minutes to hours; using diameter instead of radius in area and volume formulas.
Key points
- Successive percentage changes multiply.
- Discount is on marked price; profit is on cost price.
- Convert km/h to m/s using 5/18.
- Use approximation to eliminate options in data interpretation.