Question:
The volume of a sphere is 38808 cm3. Its curved surface area is
(a) 5544 cm2
(b) 8316 cm2
(c) 4158 cm2
(d) 1386 cm2
Solution:
(a) $5544 \mathrm{~cm}^{2}$
Let r cm be the radius of the sphere.
Then we have:
$\frac{4}{3} \pi r^{3}=38808$
$\Rightarrow r^{3}=\frac{38808 \times 3 \times 7}{4 \times 22}=9261$
$\Rightarrow r=21 \mathrm{~cm}$
$\therefore$ Curved surface area $=4 \pi r^{2}=4 \times \frac{22}{7} \times 21 \times 21$
$=5544 \mathrm{~cm}^{3}$