ratio??

Let x and y be the radii of two spheres respectively.

Since all sphere are similiar,

x^2:y^2=729:64
(x:y)^2=729:64
x:y=sq.root(729:64)
x:y=sq.root(729):sq.root(64)
x:y=27:8

so the ratio of their radii is 27:8