Question

If CSA of a sphere is 154 $c{m}^2$, then its radius is ___ cm.

• A. 3.5

Answer 1

The correct option is A 3.5
CSA of sphere = 4πr${}^2$
$\Rightarrow 154=4\times \frac{22}{7}\times r^2$
$\Rightarrow r^2=\frac{154\times 7}{88}$
$\Rightarrow r^2=\frac{49}{4}$
$\Rightarrow r^2=(\frac{7}{2}{)}^2$
$\Rightarrow r=\frac{7}{2}$

Therefore, r = 3.5 cm