Question 49233
Try making a table:

{{{2^3 = 8}}}
{{{3^3 = 27}}}
{{{4^3 = 64}}}
{{{5^3 = 125}}} Too much!

If you built a 4X4X4 cube you would use 64 of the 100 cubes.
If you built a 5X5X  cube you would use 125 cubes, but you have only 100.