SOLUTION: If 1 gallon of paint covers 400 square feet, about how many gallons of paint are needed to paint the outside of a spherical tank of diameter 20 feet?

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Question 206149: If 1 gallon of paint covers 400 square feet, about how many gallons of paint are needed to paint the outside of a spherical tank of diameter 20 feet?
Answer by Targetweek(62) About Me  (Show Source):
You can put this solution on YOUR website!
SA of a sphere is given by...
- SA+=+4+%2Api+%2Ar%5E2
Since the radius is half of the diameter (20), r = 10
Next plug the value in
- SA+=+4+%2Api+%2Ar%5E2
- SA+=+4%2Api%2A%2810%29%5E2
- SA+=+4%2Api%2A100
- SA+=+400%2Api
= SA+=+1256.64ft%5E2
Then divide SA by 400
and you get 3.14
Assuming that you buy 1 gallon cans of paint it would take 4 cans but it you want the exact number then it would be 3.14 gallons