Math CentralQuandaries & Queries


Question from Frank, a parent:

How many cubic feet are there in a  pipe with  8 inch inside diameter and ten feet long.
Thank you

Hi Frank.

The volume of a cylinder (a pipe is a cylinder) is (pi)r2h. Where (pi) is about 3.1416, r is the radius (half the diameter) and h is the length (or height).

Since you want cubic feet, you must first convert your measurements all to feet: 8 inches = (2/3) feet.

Now get the radius: that's (1/2)(2/3) = (1/3) feet.

Now put these values into the equation I gave at the beginning: Volume = (3.1416)(1/3 feet)2(10 feet)

On my calculator, I get 3.49 cubic feet.
Stephen La Rocque.

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