Question

The diameter of the driving wheel of a bus is 140 cm. How many revolutions per minute must the wheel make in order to keep a speed of 66 km per hour ?

Answer 1

Speed of the bus = 66 km/hr

Distance covered by the wheel in one minute = $\frac{66\times 1000\times 100}{60}=110000$ $cm$

Circumference of the wheel = $2\times \frac{22}{7}\times 70=440$ $cm$

Therefore, distance covered by the wheel in one revolution = $440$ $cm$

Hence, number of revolutions in one minute = $\frac{110000}{440}=250$