The GMAT Sample Math question is from the topic Mensuration.
A wheel of a car of radius 21 cms is rotating at 600 RPM. What is the speed of the car in km/hr?
A. 79.2 km/hr
B. 47.52 km/hr
C. 7.92 km/hr
D. 39.6 km/hr
E. 3.96 km/hr
The correct choice is (B) and the correct answer is 47.52 km/hr.
The radius of the wheel is 21 cms.
Therefore, in one revolution, the wheel will cover a distance of
= 132 cms.
In a minute, the wheel will cover a distance of 132 * 600 = 79200 cms.
In an hour, the wheel will cover a distance of 79200 * 60 = 4752000 cms.
Therefore, the speed of the car = 4752000 cms/hr = 47.52 km/hr