A cylindrical container holds three tennis balls. The diameter of the container is 3 inches, and it’s height is 8.5 inches. The diameter of each ball is 2.5 inches. What is the unused volume of the container when it is holding all three balls ?

35.540 cubic inches
First we find the volume of the cylindrical container: Â
V = Ï€(r^2)h Â
d = 3 Â
r = 3/2 = 1.5 Â
V = π(1.5^2)(8.5)
= 60.083 cubic inches Â
Then we  find the volume of three tennis balls: Â
volume of one ball (sphere): Â
V = (4/3)Ï€(r^3) Â
d = 2.5 Â
r = 2.5/2 = 1.25 Â
V = (4/3)Ï€(1.25^3) = 8.181 Â
volume of three spheres: Â
3 × V = 3 × 8.181
= 24.543 cubic inches Â
Then we get the difference to find the unused volume of the container: Â
60.083 - 24.543 = 35.540 cubic inches