Math CentralQuandaries & Queries


Question from ed, a parent:

i have a piece of sheet metal 56' 6" long what is the size of the circle it would make?

Hi Ed,

I assume you want to roll up the piece of metal to form a circular cylinder.


The circle will thus have a circumference of 56 ft 6 in or 678 inches. The circumference of a circle is

2 π r

where r is the radius and π is approximately 3.1416. Thus you have

678 = 2 π r

and thus

r = 678/(2 π) = 107.91 inches

12 × 9 = 108 so the radius of the circle is very close to 9 ft.

We are curious about what you are making. Can you tell us?


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