1. The problem statement, all variables and given/known data The problem states to calculate the height at which the gravity acceleration is 5x smaller than on the surface of the earth. So g=9,81 m/s^2 R=6370km M=6x10^24 gamma(don't know how to put it :P)=6,67x10^-11 2. Relevant equations g=gamma x M/(R+h)^2 3. The attempt at a solution I was pretty confident in this h = sqrt (g x R)/(gamma x M) but the result turned out bad. The book I use states that the result is 7874 km.