Question

The diameter of a wheel of a bus is $90$ cm which makes $315$ revolutions per minute. Determine its speed in kilometer per hour. (Use $\pi =\frac{22}{7}$)

Answer 1

$\Rightarrow$ Diameter of wheel $=90cm$

$\Rightarrow$ Radius of wheel $\left(r\right)=\frac{90}{2}cm=45cm$

$\Rightarrow$ Distance covered in $1$ revolution $=2\pi r$

$\Rightarrow$ Distance covered in $1$ revolution $=2\times \frac{22}{7}\times 45=\frac{1980}{7}cm$

$\Rightarrow$ Distance covered in $315$ revolutions $=\frac{1980}{7}\times 315=89100cm=891m$

$\Rightarrow$ Hence, the speed is $891m/min=\frac{891}{1000}\times 60km/hr=53.46km/hr$