Math CentralQuandaries & Queries

Question from charlie:

I have a tank that is 10 feet in diameter that I want to put floating degreaser in.The rate for the degreaser is 1/2 gallon per square foot of surface water.How do I figure out how many gallons I need?


The area of a circle is π r2 where r is the radius and π is approximately 3.14159. Thus for your circular surface the area is

π r2 = π 52 = 78.54 square feet.

At 1/2 a gallon per square foot that's

78.54/2 = 39.27 gallons.


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