Question

Diameter of a sphere is $21$ dm. Find its surface area.

• A. $1286d{m}^2$
• B. $1376d{m}^2$
• C. $1386d{m}^2$
• D. $1380d{m}^2$

Answer 1

Answer: (C)

$1386d{m}^2$

Given, diameter of a sphere, $d=21$ dm,

$\therefore$ radius of the sphere, $r=\frac{d}{2}=\frac{21}{2}=10.5$ dm
Surface area of sphere $=4\pi r^2$

$=4\pi (10.5{)}^2=4\times \frac{22}{7}\times (10.5{)}^2$

$=1386d{m}^2$.

Therefore, option $C$ is correct.