Question

To save money at tennis pro company has manufactured a cylindrical tube that exactly fits three tennis balls if the diameter of the tube is 6.5 cm what is the volume of the air in the tube 

Answer 1

Volume of air = volume of the cylinder - volume of 3 tennis balls
As the balls fit exactly into the tube we have:
Diameter of the tube = 6.5 cm so the radius = 3.25 cm. This is also the radius of the balls.
The height of the cylinder 3*6.5 = 19.5 cm.
So, volume of air
= pi*3.25^2*19.5 - 3*pi*3.25^2
= 99.55 cm^2 to nearest hundredth.