Question

Find the area of a ring shaped region enclosed between two concentric circles of radii $20$ cm and $15$ cm.

• A. $175\pi c{m}^2$
• B. $75\pi c{m}^2$
• C. $275\pi c{m}^2$
• D. $750\pi c{m}^2$

Answer 1

The correct option is A $175\pi c{m}^2$

We know that area of a circle is $\pi r^2$, where $r$ be a radius of the circle.

Let us assume $R=20$ $cm$ & $r=15$ $cm$

$\therefore$ Required area $=\pi (R^2-r^2)=\pi ({20}^2-{15}^2)=175\pi c{m}^2$.