Question 2176
right, i am getting there slowly :-)

You have a cylinder which is hollow? and balls of cement (or whatever) are added to the mill?

Now, is the cyclinder filled with balls, until no more can be fitted in?

Assume each ball is the same but do not know the dimensions of it...then we will have to theorise on the volume of a ball by 4/3pi*r^3 and know how many it takes to fill the mill, then work out their total volume then calculate the mill volume, from its cross-sectional area times its length.

Then just work out the percentage of the total area taken up by the balls.

Hope this helps. If not, explain some more please :-)

Jon