Mass of the Earth
g = G*Mearth/Rearth2 or Mearth = g*Rearth2/G
= 9.8 m/s2 * (6.4 x 106 m)2 / 6.67 x 10-11 Nt-m2/kg2
This value is certainly large as we expect the mass of the earth to be large. But is there another way to get the same answer? If there is, that would greatly add to our confidence in our answer!