A woman weighs 125 lbs on the surface of the earth ( radius = 3960 miles). At what distance above the surface of the earth would she weigh 85 lbs?
Since F = GMm/r^2,
at a height of h miles, you want
(3960+h)^2/3960^2 = 125/85
at a height of h miles, you want
(3960+h)^2/3960^2 = 125/85