A hemispherical bowl is made of steel 0.5 cm thick.
Question:

A hemispherical bowl is made of steel 0.5 cm thick. The inside radius of the bowl is 4 cm. Find the volume of steel used in making the bowl.

Solution:

Internal radius of the hemispherical bowl = 4 cm
Thickness of a the bowl = 0.5 cm
Now, external radius of the bowl = (4 + 0.5 ) cm = 4.5 cm

Now, volume of steel used in making the bowl =  volume of the shell

$=\frac{2}{3} \pi\left(4.5^{3}-4^{3}\right)$

$=\frac{2}{3} \times \frac{22}{7} \times(91.125-64)$

$=\frac{2}{3} \times \frac{22}{7} \times 27.125$

$=56.83 \mathrm{~cm}^{3}$

∴ 56.83 cm3 of steel is used in making the bowl .