Question

you find your mass to be 42 kg on a weighing machine.Is your mass more or less than 42 kg?

Answer 1

When we stand on a weighing machine, it measures our apparent weight .
Because when we stand on the machine, weight acts in the downward direction and upthrust due to air acts in the upward.
So, due to upthrust , the body appears to loose some weight.

Conclusion : The mass indicated in weighing machine[42kg] is less than the actual mass 

Answer 2

When we stand on a weighing machine , then the air exerts an upward force on our body and makes us slightly lighter than we actually are. So, if a weighing machine shows our mass to be 42 kg, then or actual mass will be slightly more than 42 kg