Question

The radii of two concentric circles are 19 cm and 16 cm respectively. The area of the ring enclosed by these circles is

(a) 320 $c{m}^2$ (b) 330 $c{m}^2$
(c) 332 $c{m}^2$ (d) 340 $c{m}^2$

Answer 1

Area of ring = $\pi (R^2-r^2)$

$=\frac{22}{7}\times (R^2-r^2)$

$=\frac{22({19}^2-{16}^2)}{7}$

$=\frac{22(361-256)}{7}$

$=\frac{22\times 105}{7}$

$=22\times 15=330cm²$