Solution: The volume of a sphere is $ \frac43\pi y^3 $, and the volume of a hemisphere is $ \frac23\pi (3y)^3 = \frac23\pi \times 27y^3 = 18\pi y^3 $. The ratio is $ \frac\frac43\pi y^318\pi y^3 = \frac454 = \frac227 $. \boxed\dfrac227 - Abu Waleed Tea