Question

The diameter of a roller is 84 cm and its length is 120 cm. It takes 500 complete revolutions to move once over to level a playground. Find the area of the playground in square metres.

Answer 1

Radius of the cylindrical roller = $\frac{84}{2}$ = 42 cm
Length of the roller = 120 cm
So, curved surface area of the roller = $2\mathrm{\pi }rh$
$$\begin{gathered} =2\times \frac{22}{7}\times 42\times 120 \\ =31680{\mathrm{cm}}^2 \end{gathered}$$

Area covered by the roller in 1 revolution = 31680 cm²
Area covered by the roller in 500 revolution = $500\times$31680 = 15840000 cm²

= 1584 m²