Question

calculate earth's mass given the acceleration due to gravity at the North pole is 9.830 m/s² and the radius of the earth is 6371km from pole to pole.

Answer 1

$$g=G\frac{M}{R^2}$$

$$M=gR^2/G\\ =9.8*(6371*10^3)^2/(6.67*10^{-11})\\ =5.96*10^{24}\:\rm kg$$