EXAMPLE: An open tank made of iron 1/4 inch thick, is 4 feet long, 2
feet 6 inches broad, and 2 feet deep, outside measurement. Assuming that
iron weighs 7.8 times as much as water, find the weight of the tank.
The external volume of the tank = 2 × 2-1/2 × 4 cubic feet = 20 cubic
feet.
Since the iron is 1/4 inch thick, the inside length is 1/2 inch less
than the outside, the inside breadth is 1/2 inch less than the outside,
and the inside depth is 1/4 inch less than the outside.