Calculating Earth Masses in a Planet with Earth-Size and Moon-Density

[brianh]

"Earth Masses"

I've been stuck on a problem for a few days now, and I know that it is a lot easier than I am making it out to be. My goal is to find how many Earth masses lie within a planet who has the same size as Earth, and the same density as the moon.

I honestly do not know how to go about this problem. Could anybody give me any guiding tips?

 

[granpa]

density is mass per unit volume

an object the same size as Earth has the same volume as earth

define your unit volume as one Earth volume

 

[The legend]

compare densities of Earth and moon ... that's almost all in a way!