1 gallon of paint covers area = 400 square feet
Diameter of spherical tank = 20 feet
Radius = [tex]\frac{20}{2}=10[/tex]
Surface area of sphere is = [tex]4\pi r^{2}[/tex]
SA= [tex]4\times3.14\times10\times10[/tex] = 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 =
[tex]\frac{1256}{400}=3.14[/tex]
Hence, 3.14 gallons of paint is required to paint the outside of the spherical tank.
