The GMAT Sample Math question for the day is from the topic Mensuration.

Question
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.

Explanatory Answer
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

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