The radius of a wheel of a bus is 45 cm. Determine its speed in kilometres per hour, when its wheel makes 315 revolutions per minute

Explanation

Radius of wheel of bus = 45 cm
`:.` Circumference of the wheel `= 2 pi r`
`= 2 xx (22)/(7) xx 54 = (1980)/(7) cm`
`:.` Distance covered by the wheel in one revolution `= (1980)/(7) cm`
Distance covered by the wheel in 315 revolutions `= 315 xx (1980)/(7)`
`45 xx 1980 = 89100 cm`
`= (89100)/(1000 xx 100) km = (891)/(1000) km`
`:.` Distance covered in 60 minutes or 1 hr `= (891)/(1000) xx 60 = (5346)/(100) = 53.46 km`
Hence, speed of bus = 53.46 km/hr