Molecular weight of 60s sub unit = 2.7 x 10^6 units
Molecular weight of 40s sub unit = 1.3 x 10^6 units
Densities are same and both are spherical
Relative size = Molecular weight of 60s / molecular weight of 40s = 2.7 x 10^6 / 1.3 x 10^6 = 27/13 = 2.0769