The surface area of a sphere is frac 792 7 cm 2... - WAEC Mathematics 2018 Question

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

\(4 \pi r^2\) = \(\frac{792}{7}cm^2\)

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\(cm^3\) (to the nearest whole number)