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.
Given,
In-radius of bowl (ri) = 4 cm
Thickness of steel = 0.5 cm
External radius of bowl (re)= 4 + 0.5 = 4.5 cm
Volume of metal = 
πre3 – 
ri3
= 
(re3 – ri3) = 
3 – 43) = 
= 
= 56.83 cm3
24