The weight of the other person has to be the same in order for the seesaw to be balanced, then the person on the other side weighs 100 pounds as well. Now, we know that:
[tex]1\text{ lb=}0.45\text{ kg}[/tex]
Then to find the mass we just multiply the weight in pounds by 0.45:
[tex]100\cdot0.45=45[/tex]
Therefore the other person has a mass of 45 kg.
