Quantitative Aptitude
What TANCET tests here
Quantitative Aptitude is arithmetic-heavy: percentages, ratio and proportion, profit and loss, simple and compound interest, time-speed-distance, time and work, averages and mixtures, with a smaller set of algebra, number-system, geometry/mensuration, permutation-combination and probability items. The exam rewards fast, exact setup more than long calculation.
Core rules
- Convert every comparison to a base: 'A is 25% more than B' means A = 1.25B, so B is 20% less than A.
- Successive percentage changes multiply: net multiplier = (1 ± a)(1 ± b), never a + b.
- For average speed over equal distances, use the harmonic mean: 2xy/(x+y).
- Time and work: convert to rates; if A finishes in x days and B in y days, together they take xy/(x+y) days.
- Simple interest is linear; compound interest compounds each period. For two years, CI − SI = P(r/100)^2.
- In ratio problems, introduce a common multiplier k and keep units consistent.
Worked example
A shopkeeper marks an article 40% above cost and offers successive discounts of 10% and 5%. What is the net profit percentage? Take cost = 100. Marked price = 140. After 10% discount: 140 × 0.90 = 126. After a further 5%: 126 × 0.95 = 119.7. Profit = 19.7 on cost 100, so 19.7%. The total discount is 14.5%, not 15%: the second discount applies to the reduced price, not the marked price.
Traps that cost marks
- Adding successive percentages (10% + 5% = 15%) instead of multiplying.
- Computing profit on selling price rather than cost price.
- Using the arithmetic mean for average speed.
- Mixing units (km/h with metres, months with years in interest).
- Rounding mid-calculation and then choosing an option that differs by a small margin.