Math CentralQuandaries & Queries


Question from Denise, a parent:

I need to know the measurement of an octagon on the inside from flat side to side side, not angle to angle, where the sides are 10 feet long. My husband and I have been out of school too long and it's true what they say, if you don't use it, you lose it. We definitely lost our math skills. Thanks

Hi Denise,

Look at Stephens response to Martin's question about an octagon. In this response Stephen shows that the width of a regular octagon w and the length of a side x are related by

x = 0.4142w.

Let's do this in inches. You have x = 10 feet which is 120 inches so

0.4142w = 120

and thus

w = 120/0.4142 = 289.7056 inches.

But 24 feet is 288 inches so w = 24 feet and 1.7056 inches which is very close to 24 feet 1 and 11/16 inches.


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