JAMB 2018 · UTME · Q36

The volume of a hemispherical bowl is $718\frac23\text{ cm}^3$ . Find its radius. $\left[\text{Take }\pi = \frac{22}{7}\right]$

Worked solution (try it first)

A hemisphere is half a sphere, so its volume is $\frac23\pi r^3$ .
Write $718\frac23$ as $\frac{2156}{3}$ .
$\frac23 \times \frac{22}{7} \times r^3 = \frac{2156}{3}$ , so $r^3 = \dfrac{2156 \times 7}{44} = 343$ .
Take the cube root: $r = 7.0$ cm, option C.