We have the next information
The moment of a force about the fulcrum is equal to the balance of the seesaw so in order to know the moment of force on both sides of the fulcrum must be the same in order to balance.
so we have the next equation
[tex]m1\cdot g\cdot d1=m2\cdot g\cdot d2[/tex]m1=mass one
m2=mass two
d1=distance 1
d2 distance 2
in our case we have
m1= 40 kg
d1=2m
m2=30 kg
d2=?
we substitute the values given in the formula above
[tex](40)(9.8)(2)=30(9.8)(d2)[/tex]then we isolate d2
[tex]40(2)=30d2[/tex][tex]d2=\frac{40(2)}{30}=2.67m[/tex]Hence the girl sit 2.67m from the fulcrum
