Question

The wheel of a cart is making 5 revolutions per second. If the diameter of the wheel is 84 cm, find its speed in km per hour.

Answer 1

Distance covered in 1 revolution$=\mathrm{\pi }\times d$
$$\begin{gathered} =\left(\frac{22}{7}\times 84\right)\mathrm{cm} \\ =264\mathrm{cm} \end{gathered}$$
Distance covered in 1 second$=\left(5\times 264\right)\mathrm{cm}$
= 1320 cm
Distance covered in 1 hour$=\left(60\times 60\times 1320\right)\mathrm{cm}$

$$\begin{gathered} =4752000\mathrm{cm} \\ =\left(\frac{4752000}{1000\times 100}\right)\mathrm{km} \\ =47.52\mathrm{km} \end{gathered}$$