1. The problem statement, all variables and given/known data Consider a hypothetical extra*solar world, planet X, that has 2.2 times the radius of the Earth and 2.5 times its density. What is the acceleration due to gravity on the surface of planet X? 2. Relevant equations g=GM/r^2 3. The attempt at a solution I am not sure what to do with density. I know that mass/volume = density, but how do I solve the equation without mass? I know how to solve the equation when I know mass but if I only know density, how do I solve it?