Math CentralQuandaries & Queries


Question from lee, a parent:

if you have a 46 acre round reservoir, how far around in feet would that be ??

Hi Lee,

There are 43560 square feet in an acre so 46 acres is 46 × 43560 = 2003760 square feet.

The area of a circle is given by π r2 where r is the radius. Hence

2003760 = π r2


r2 = 2003760/π = 637816.62 square feet

and hence

r = √637816.62 = 798.63 feet.

The circumference of a circle is given by 2 π r and hence the circumference of the reservoir is

2 π × 798.63 = 5017.97 feet.


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