The ball can be modeled as a sphere.
The volume of a sphere is given by:
V = (4/3) * pi * r ^ 3
Where,
r: radius of the sphere.
We have then:
V = (4/3) * pi * (18/2) ^ 3
V = 3053.6 in ^ 3
Answer:
the volume of a beach ball with a diameter of 18 inches is:
V = 3053.6 in ^ 3