At a certain distance above the surface of the Earth, the graviational force on an object is reduced to 18% of its value at Earth's surface. Determine this distance and express it as a multiple of Earth's radius. FYI the Earth's mass is 5.98x10^24 kg and the Earth's radius is 6.38x10^6 m What I did was this: Gmm/r² = (Gmm/r²)(9/50) The left side is the gravitational force on the object at the surface of the Earth and the right side is %18 of that force (radius is unkown). Since Gmm is constant in both i came up with: 1/r² = 9/50r² 1/6.38x10^6 = 9/50r² r = 1070m But I don't understand what they mean in by a multiple of Earth's radius. In the back of my book the answer is 1.4 Re. Is my answer wrong? Or do I just need to take it another step? Thanks for any help!