Numerical Ability & Quantitative Aptitude Flashcards

A train 240 m long passes a pole in 12 seconds. How long will it take to pass a platform 360 m long?

Answer: 30 seconds

Speed = 240/12 = 20 m/s; total distance = 240+360 = 600 m; time = 600/20 = 30 seconds.

If 15 workers can complete a job in 24 days, how many days will 18 workers take to complete the same job?

Answer: 20 days

Using inverse proportion: 15x24 = 18xd, so d = 360/18 = 20 days.

The difference between simple interest and compound interest on Rs. 5,000 at 10% per annum for 2 years is:

Answer: Rs. 50

CI = 5000x(1.1^2 - 1) = Rs.1050; SI = 5000x0.1x2 = Rs.1000; difference = Rs.50.

A shopkeeper marks goods 40% above cost price and gives a 20% discount. His profit percent is:

Answer: 12%

SP = CP x 1.4 x 0.8 = 1.12 x CP, so profit = 12%.

The LCM of two numbers is 180 and their HCF is 12. If one number is 36, the other number is:

Answer: 60

Product of two numbers = LCM x HCF = 180x12 = 2160; other number = 2160/36 = 60.

A mixture contains milk and water in the ratio 5:1. If 6 litres of water is added, the ratio becomes 5:2. Find the initial quantity of milk.

Answer: 30 litres

Let milk = 5x, water = x; after adding 6 L water: 5x/(x+6) = 5/2 gives x = 6, milk = 30 litres.

If the radius of a circle is increased by 50%, by what percent does its area increase?

Answer: 125%

New area = pi x (1.5r)^2 = 2.25 x pi x r^2; increase = 125% of original area.