Question

Find the area of a ring whose outer and inner radii are respectively 23 cm and 12 cm.

Answer 1

Area of ring = $\pi (r_1^2-r_2^2)=$

$=\frac{22}{7}\left[\right(23{)}^2-\left(12{)}^2\right]$

$=\frac{22}{7}\times 385=120c{m}^2$