WAEC Mathematics 2018 Paper

Surface area of a sphere = $4 \pi r^2$

$4 \pi r^2$ = $\frac{792}{7} \text{cm}^2$

4 x $\frac{22}{7}$ x $r^2$ = $\frac{792}{7}$

$r^2$ = $\frac{792}{7}$ x $\frac{7}{4 \times 22}$

= 9

r = $\sqrt{9}$

= 3cm

Hence, volume of sphere

= $\frac{4}{3} \pi r^3$

= $\frac{4}{3} \times \frac{22}{7} \times 3 \times 3 \times 3$

= $\frac{4 \times 22 \times 9}{7}$

$\approx$ = 113.143

= 113$\text{cm}^3$ (to the nearest whole number)