Question

Find the area of the washer formed by two concentric circles with outer radii and inner radii as $4\text{cm}$ and $3\text{cm}$ respectively.

Answer 1

Given $\Rightarrow$ $R=4\text{cm}$

$r=\text{cm}$

$\begin{array}{cc}\text{Area of the washer}& =\pi \left(R^2-r^2\right)\\ & \\ & =\frac{22}{7}\left(4^2-3^2\right)\\ & \\ & =\frac{22}{7}\left(7\right)\\ & \\ & =22{\text{cm}}^2\end{array}$

Hence, the area of the washer is equal to $22{\text{cm}}^2$.