Question

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 1

1 gallon of paint covers area = 400 square feet

Diameter of spherical tank = 20 feet

Radius =
`(20)/(2)=10`

Surface area of sphere is =
`4\pi r^(2)`

SA=
`4*3.14*10*10` = 1256 square feet

Now, according to the question, 400 sq feet area is covered in 1 gallon

So, 1256 square feet will be covered in =

`(1256)/(400)=3.14`

Hence, 3.14 gallons of paint is required to paint the outside of the spherical tank.