Tough physics question help... (Gravitational force)?

Use the formula F = G (M1 M2) / rE^2 Substitute what you know at the two points into the equation to get two separate equations. F1 = G*Me*M/ (1.5rE)^2 F2 = G*Me*0.5M / (2.4rE)^2 (I used Me for the m of the earth) The ratio of F2 to F1 will be F2 divided by F1. When you divide, all the unknown variables cancel. Alternatively, since the force is directly proportional to the m, halving the m halves the force. But the force is also inversely proportional to the square of the distance. So if you move 2.5/1.5 times father away, it reduces the force by a factor of (2.5/1.5)^2. So the new force will be 0.5 * (2.5/1.5)^2 times the old force. If you do it the first way I told you, you'll see that this is exactly what you get after the unknown variables cancel.