Everything seems to make sense to me, but I know the answer is wrong.. "Actually, mass and weight are not the same thing. Mass is how much of something there is - which does not change throughout the universe (mass = density * volume). Weight is a force, which is constantly changing throughout the universe depending on the acceleration of gravity (weight = mass * acceleration of gravity). You can work out a persons mass simple by dividing their weight by 9.806 (Earth's acceleration of gravity). For example, if your weight = 80 kilograms, then your mass would be 8.15 kilograms. Because -- 80 kilograms / 9.806 = 8.15 kilograms"