Question:
If the lateral surface of a cylinder is $94.2 \mathrm{~cm}^{2}$ and its height is $5 \mathrm{~cm}$, find:
(i) radius of its base
(ii) volume of the cylinder [Use pi = 3.141]
Solution:
(i) Given,
Height of the cylinder = 5 cm
Let radius of cylinder be 'r'
Curved surface of the cylinder $=94.2 \mathrm{~cm}^{2}$
$2 \pi \mathrm{rh}=94.2 \mathrm{~cm}^{2}$
$r=3 \mathrm{~cm} \quad[\pi=31.4, h=5 \mathrm{~cm}]$
(ii) Volume of the cylinder $=\pi r^{2} h=\left(3.14 \times 3^{2} \times 5\right) \mathrm{cm}^{3}=141.3 \mathrm{~cm}^{3}$