A boy is cycling such that the wheel 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.

Explanation

Given the diameter of the wheel d= 60 cm

Distance covered by the wheel in 1 revolution = Circumference of the wheel

Distance covered by the wheel in 1 revolution =` pi xx d = (22/7)xx 60 cm`

Distance covered by the wheel in 140 revolutions `= 22/7 xx 60 xx 140= 26400 cm`

Thus, the wheel covers 26400 cm in 1 minute.
`:.` speed = ` (26400/100 ) xx60 m/(hr)`

`:.` speed = ` (264 xx 60)/1000 (km)/(hr)`

`:.` speed = `15.84 (km)/(hr)`