Question

A boy is cycling with a banner of "Say No to Crackers' such that the wheels of the cycle are making 140 revolutions per minute. If the diameter of the wheel is 60 cm. Calculate the speed per hour which the boy is cycling.

Answer 1

Circumference of wheel $2\times \pi \times r=\pi \times d=\frac{22}{7}\times 60=\frac{1320}{7}cm$
$\therefore$ In 1 revolution it travels $=\frac{1320}{7}cm$
In 140 revolution it travels $=\frac{1320}{7}\times 140=26400cm$
This 26400 cm is done in 1 minute.
$\therefore$ In 60 minute (1hr) $=26400\times 60cm$
$=1584000cm$
$=15.84km$
$\therefore$ Speed is 15.84 km/hr