SOLUTION: How many feet of piping can be made from 5 cubic feet of iron if the outer diameter of the pipe is 16 inches and the inner diameter is 12 inches?

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Question 1050239: How many feet of piping can be made from 5 cubic feet of iron if the outer diameter of the pipe is 16 inches and the inner diameter is 12 inches?
Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
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How many feet of piping can be made from 5 cubic feet of iron if the outer diameter of the pipe is 16 inches and the inner diameter is 12 inches?
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Your guiding equation is

5 = pi%2A8%5E2%2AL+-+pi%2A6%5E2%2AL.   (1)

pi%2A8%5E2%2AL is the volume of the cylinder of the radius 8 = 16%2F2 inches and the length of L feet.

pi%2A6%5E2%2AL is the volume of the cylinder of the radius 6 = 12%2F2 inches and the length of L feet.

The difference is the volume of the pipe, which is a hollow cylinder.

The number "5" in the left side of the equation (1) is the given volume of the iron.

Simplify (1):

5 = pi%2AL%2A%2864-36%29 = pi%2AL%2A28,

hence

L = 5%2F%2828%2Api%29.

Use your calculator.