Question

Please help! I don’t know how to solve this; it’s a practise question from a past exam.

Answer 1

Volume of cylinder is given by:
V=πr²h
where:
r=radius
h=height
suppose the radius of the large cylinder is r, since the cylinder has been filled with the 5 balls, the height of the cylinder is:
5d where d is the diameter of one ball, but d=2r:
hence the height will be:5(2r)=10r
Thus the volume of the cylinder will be:
3925=3.14×r²×10r
3925=31.4r³
hence solving for r we shall obtain:
r³=125
hence
r=∛125
r=5 cm

Answer: r =5 cm