During recess, Tom and his little sister Marcie want to play on the see-saw. Tom is quite a bit heavier than Marcie. Where should they sit so the see-saw is balanced

Tom has to sit more towards the middle (fulcrum) while Marcie sits on the edge of the seesaw.

Explanation:

Since Tom is heavier than Marcie, he has to sit towards the middle of the seesaw while Marcie sits on the edge. This is what is going to help to distribute both weights on the seesaw.

If they both sat on the edges of the seesaw, Tom's weight is going to hit the ground fast and this will end up causing Marcie to suspend in the air, since Marcie does not have enough body weight required to match Tom's own in order for the see saw to move uniformly, up and down.