A spherical water tower has a diameter of 20 feet. (use the value pi=3.143) Aproximately how many cubic fee of water does it contain when it is 3/4 full?
The volume of a spherical water tower is
V = 4/3·pi·(D/2)³ = 4/3·pi·(20/2)³ = 4/3·pi·1000 feet³.
So, a tower contains
3/4·V = 3/4·4/3·pi·1000 = 1000·pi ≈ 1000·3.143 = 3143 feet³
of water when it is 3/4 full.