Solution: The volume of the sphere is $ \frac43\pi (2x)^3 = \frac323\pi x^3 $. The volume of the hemisphere is $ \frac23\pi (3x)^3 = 18\pi x^3 $. The ratio is $ \frac32/318 = \frac3254 = \frac1627 $. The ratio of their volumes is $\boxed\dfrac1627$. - Nelissen Grade advocaten