Given that the ball has a thickness of 1 cm and the radius at the outside is 5 cm, thus the radius from inside is 5 - 1 = 4cm.
The approximate volume of rubber used to make the ball is given by the volume of the ball at the outside surface minus the volume of the ball at the inside surface.
i.e.
[tex]Volume\ of\ rubber= \frac{4}{3} \pi\left(5^3-4^3\right) \\ \\ =
\frac{4}{3} \pi(61)= \frac{244}{3} \pi\approx255.5\ cm^3[/tex]
