Question

A man weighs 180lb on the earth's surface. What would he weigh at a distance from the center of the earth of 3times the radius of the earth?

Answer 1

$$W=G\frac{mM}{R^2}\\W'=G\frac{mM}{(3R)^2}=\frac{W}{9} \\W'=\frac{180}{9}=20\ lb$$