Quantitative Aptitude Flashcards

The speed of a boat in still water is 15 km/h. The current speed is 3 km/h. What is the ratio of upstream to downstream speed?

Answer: 2:3

Upstream = 12 km/h, downstream = 18 km/h; ratio = 12:18 = 2:3.

A rectangle has a perimeter of 56 cm. If its length is 3 times its width, what is the area?

Answer: 147 cm²

2(l+w)=56 → l+w=28; l=3w → 4w=28 → w=7, l=21; area=21×7=147 cm².

A sum of money doubles itself in 8 years at simple interest. What is the annual rate of interest?

Answer: 12.5%

SI = P in 8 years; P = P×R×8/100 → R = 100/8 = 12.5%.

In how many ways can 4 books be arranged on a shelf from a collection of 7 different books?

Answer: 840

This is a permutation: P(7,4) = 7!/(7−4)! = 7×6×5×4 = 840.

A man spends 30% of his salary on rent, 20% on food, and saves the rest. If he saves $2,100, what is his salary?

Answer: $4,200

He saves 50% of salary; 0.50 × salary = $2,100 → salary = $4,200.

What is the value of (0.125)^(−1/3)?

Answer: 2

0.125 = 1/8 = 2⁻³; (2⁻³)^(−1/3) = 2^(3/3) = 2¹ = 2.

Two numbers are in the ratio 7:5. If their difference is 18, what is the larger number?

Answer: 63

7x − 5x = 2x = 18 → x = 9; larger number = 7×9 = 63.