A hemispherical tank is made up of an iron sheet 1 cm thick. If the inner radius is 1 m, then find the volume of the iron used to make the tank.

The internal radius of hemispherical tank r = 1 m and thickness 1 cm = 0.01 m
Therefore, the outer radius R = 1 + 0.01 = 1.01 m
Volume of hemispherical tank = 2/3π(R³ – r³)
= 2/3 × 22/7 × [(1.01)³ -1³]
= 2/3 × 22/2 × (1.030301 – 1)
= 2/3 × 22/7 × 0.030301
= 0.06348 m³
Hence, the volume of the iron used to make the tank is 0.06348 m³.