1. The problem statement, all variables and given/known data Calculate the mass and radius of a black hole with density 750 kg/m^3. 2. Relevant equations 3. The attempt at a solution In a previous question, I already used the Schwarzchild radius to come up with a formula for the density of a black hole: D = (mass/(4/3pi((2Gmass/c^2)^3). I realize that this should be enough to solve for mass, but I am having difficulty with the algebra...How do I solve for mass when one of the "mass" variables is stuck inside the Scharzchild radius in a complicated fraction?