Question:
A closed cylindrical tank of diameter 14 m and height 5 m is made from a sheet of metal. How much sheet of metal will be required?
Solution:
Diameter $=14 \mathrm{~m}$
Radius $=\frac{14}{2}=7 \mathrm{~m}$
Height $=5 \mathrm{~m}$
$\therefore$ Area of the metal sheet required $=$ total surface area
$=2 \pi \mathrm{r}(\mathrm{h}+\mathrm{r})$
$=2 \times \frac{22}{7} \times 7(5+7) \mathrm{m}^{2}$
$=44 \times 12 \mathrm{~m}^{2}$
$=528 \mathrm{~m}^{2}$