jmc

Question

A pipe with inside diameter 10'' is to carry water from a reservoir to a small town in an arid land. Neglecting the friction and turbulence of the water against the inside of the pipes, what is the minimum number of 2''-inside-diameter pipes of the same length needed to carry the same volume of water to the arid town?

Accepted Answer

Let the length of the pipes be h. The volume of the 10-inch pipe is (5^2) (h) = 25 h cubic inches and the volume of each 2-inch pipe is (1^2)(h) = h cubic inches. Hence we see it takes exactly 25 2-inch pipes to match the volume of one 10-inch pipe. The answer is 25 pipes.