Question

A boy is cycling such that the wheels of the cycle are making $140$ revolutions per minute. If the diameter of the wheel is $60cm$, calculate the speed per hour with which the boy is cycling.

Answer 1

Radius of the wheel $=r=\frac{60}{2}=30cm$

Circumference of the wheel $=2\pi r=2\times \frac{22}{7}\times 30=\frac{1320}{7}cm$

Distance covered in $1$ revolution $=\frac{1320}{7}cm$

Distance covered in $140$ revolutions $=\frac{1320}{7}\times 140=26400cm=264m=\frac{264}{1000}km$

Distance covered in one minute $=$ Distance covered in $140$ revolutions $=\frac{264}{1000}km$

Distance covered in $1$ hour $=\frac{264}{1000}\times 60=15.84km$

Hence, the speed with which the boy is cycling is $15.84km/hr.$