The ratio of the volumes of two spheres is 64:125. What is the ratio of their radii?
All you need to solve this problem is V = c* r3 where c=(4/3)π and is a constant. If we now apply this relationship to the problem we have 64/125=(r1/r2)3 solving for the ratio of the radii gives
(r1/r2)=(64/125)1/3 =.8 or 4/5
Hope this helps