Question:
The volume of a cylinder of height 8 cm is 1232 cm3. Find its curved surface area and the total surface area.
Solution:
Height $=8 \mathrm{~cm}$
Volume $=\pi r^{2} \mathrm{~h}=1232 \mathrm{~cm}^{3}$
Now, radius $=r=\sqrt{\frac{1232}{\pi \mathrm{h}}}=\sqrt{\frac{1232 \times 7}{22 \times 8}}=\sqrt{49}=7 \mathrm{~cm}$
Also, curved surface area $=2 \pi \mathrm{rh}=2 \times \frac{22}{7} \times 7 \times 8=352 \mathrm{~cm}^{2}$
$\therefore$ Total surface area $=2 \pi \mathrm{r}(\mathrm{h}+\mathrm{r})=\left(2 \times \frac{22}{7} \times 7 \times 8\right)+\left(2 \times \frac{22}{7} \times(7)^{2}\right)=352+308=660 \mathrm{~cm}^{2}$