Question

What is the area of the circular ring included between two concentric circles of radius $14$ cm and $10.5$ cm ?

• A. $255c{m}^2$
• B. $148c{m}^2$
• C. $324c{m}^2$
• D. $269c{m}^2$

Answer 1

The correct option is D $269c{m}^2$

Let $R$ be the radius of the larger circle
Hence $R=14cm$
Let $r$ be the radius of the smaller circle
Hence $r=10.5cm$

Area of the circular ring $=$ Area of the larger circle - Area of the smaller circle

$=\pi R^2-\pi r^2$

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

$=\frac{22}{7}\times ({14}^2-{10.5}^2)$

$=269.5{cm}^2$

$\approx 269{cm}^2$