Math CentralQuandaries & Queries


Question from Kenneth:


If two water pipes are 3 feet long, but one of them has a 1 foot diameter and the second has a 1 1/2 foot diameter, what simple mathematical method can be used to determine how much faster one pipe can drain water than the other pipe?

I assume that the pipe with the 1 1/2 diameter can drain faster. I am interested in how how much faster.

(I know about the volume formula, but I am looking for something using proportions if possible.)

I thank you for your reply and answer.

Hi Kenneth.

The flow rate (assuming a constant pressure between the two situations) is proportional to the cross-sectional area. Since area is related to the diameter of the pipes, the proportion is the square of these.

i.e.: 1.52 : 12. The larger pipe should be 2.25 times as fast as the small pipe.

Hope this helps,

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