If 1 gallon of paint covers 400 sq feet, about how many gallons of paint are needed to paint the outside of...?

a sphereical tank of diameter 20 feet?If 1 gallon of paint covers 400 sq feet, about how many gallons of paint are needed to paint the outside of...?
The spheree's surface area is 4 Pi R squared = 4 Pi R^2





20 ft dia = 10 ft radius





so the surface area is 4 Pi ( 10 ^2)





= 4 Pi (100)


= 400 Pi sq ft





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So, 400 Pi/ 400 = Pi gallons or 3.14 gallons. SO you need to purchase 4 gallons, rounded up. Usually you need 2 coats, so double that to 8 gallonsIf 1 gallon of paint covers 400 sq feet, about how many gallons of paint are needed to paint the outside of...?
SA = 4蟺*r^2 = 蟺*d^2


SA = 蟺 * (20 feet)^2


SA = 蟺 * 400 sq feet


SA = 1256.63706 sq feet





1256.63706 sq feet / 400 sq feet


= 3.14159265 or 蟺 gallons