Find the volume of the can and subtract the volume of the balls to find the free space.
Using 3.14 for pi:
We know that the area of a cylinder (can) is [tex]V_c=3.14r^2h[/tex].
Our diameter is 2.7, so our radius will be half of that, 1.35.
Our height is 8.5.
Let's find the volume.
[tex]3.14\times1.35\times8.5=36.0315[/tex]
Now, we know that the volume of a sphere (tennis ball) is [tex]V=\frac{4}33.14r^3[/tex].
Our diameter is 2.5, so our radius will be half of that, 1.25.
Let's find our volume.
[tex]\frac{4}3\times3.14\times1.25^3\approx8.17708333[/tex]
We have three tennis balls, and 3 times that is 24.53125.
Now we subtract the 3 spheres' volumes from our cylinder's volume to find the empty space.
36.0315 - 24.53125 = 11.50025 in³