Given:
Diameter if the spherical tank = 20 ft.
Now,
We know,
radius = diameter / 2
= 20 / 2
= 10 ft.
Now,
The area of the spherical tank = \(4 \pi r^{2}\)
= \(4 \pi (10)^{2}\)
= \(4 * \pi *100\)
= \(1256.637061\)
= \(1256.64~ft^2-->rounded\)
Now,
According to the question,
400 ft² needs 1 gallon of paint
1 ft² needs (1 / 400) gallon of paint
1256.64 ft² needs (1 / 400) * 1256.64 gallon of paint
= 3.1416 gallon of paint
= 3.14 gallon of paint --------------> rounded
So, we need 3.14 gallon of paint
