Question

At what height above the earth’s surface the acceleration due to gravity will be 1/9th of its value at the earth’s surface ?

Answer 1

g=g(r/r+h)^2
g/9=g(6400/6400+h)^2
g/9*g=(6400/6400+h)^2
1/9=(1/3)^2=
(6400/6400+h)^2
1/3=6400/6400+h
(6400+h)*1=6400*3
6400+h=19200
h =19200-6400
h=12800km