Question

Find the area of a ring whose outer and inner radii are $19cm$ and $16cm$ respectively.

• A. $330c{m}^2$
• B. $310c{m}^2$
• C. $320c{m}^2$
• D. $350c{m}^2$

Answer 1

Answer: (A)

$330c{m}^2$

Let us given $R=19$ $cm$ & $r=16$ $cm$

Area of outer circle $=\pi {\left(19\right)}^2$
$=\frac{22}{7}\times 361$
Area of inner circle $=\pi {\left(16\right)}^2$
$=\frac{22}{7}\times 256$
$\therefore$ area of the ring $=\frac{22}{7}\times 361-\frac{22}{7}\times 256$
$=\frac{22}{7}(361-256)$
$=\frac{22}{7}\left(105\right)$
$=330c{m}^2$