Question

A ball in the shape of a sphere has a surface area of $221.76$ cm${}^2$. Calculate its diameter.

• A. $8.4cm$
• B. $7.4cm$
• C. $9.4cm$
• D. None of these

Answer 1

The correct option is A $8.4cm$

Let radius of sphere be $r$ cm.

We know, surface area of sphere $=4\pi r^2$

$⟹$ $221.76c{m}^2=4\pi r^2$

$⟹$ $r^2=\frac{221.76}{4\pi }=\frac{221.76\times 7}{4\times 22}=17.64$

$⟹$ $r=\sqrt{17.64}=4.2cm$ .

Then, diameter of the sphere, $d=2r=2\times 4.2=8.4cm$.

Therefore, option $A$ is correct.