astronomy
posted by roach .
Using the densities below, find what percentage of the Earth's mass is contained in its core. If Earth's core were adjusted in radius so that the core contained forty percent of the mass, by what factor would the radius of the Earth change compared with its actual radius? (Assume the core and mantle densities remain unchanged as the core volume is changed.)
density of:
core=9710 kg/m^3
mantle=4700 kg/m^3
Earth's mean density=5520 kg/m^3
radius of:
Earth=6400km
core=3500km

Ok so I figured out that 29% of earth's mass is contained in its core.
I just don't know how to proceed with the 2nd part of this question.