If the ratio between the radii of two spheres is 3:7, what is the ratio of their volumes?

A. 27:343
B. 9:49
C. 9:7
D. 21:49

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post