So.... the "Finding mass from a size change"-section in the Inverse Square Law Page has a little problem. That problem being that it is wrong as far as I see.
Scaling the size of an 3D object follows a cube law, not an inverse square law.
That is to say, if something grows x times larger (in length, width and height), than its volume becomes x^3 time larger and, if the density stays constant, its mass increases by the factor x^3.
To show based on the example on the page:
If you have a sphere that is 1m in diameter that ways 3000kg, then its volume is 4/3*pi*(r)^3 = 4/3*pi*(1/2)^3 = 0.5235987755982989 m^3 and its density is 3000kg / (0.5235987755982989) m^3 = 5729.577951308231793071 kg/m^3.
If you now increase the spheres diameter to 10 m, while keeping the density constant, the volume of the new sphere is 4/3*pi*(10/2)^3 = 523.59877559 m^3 = 10^3 * 0.52359877559 m^3 and hence its mass is 5729.577951308231793071 kg/m^3 * 523.59877559 m^3 = 3 000 000 kg = 10^3 * 3000kg.
So you scaled it up by 10 and the volume and mass became 10^3 times larger.
Sooo... considering that this is no inverse square law we should delete that section from the page. If calculations used that formula they would have to get fixed.