You are with 17 other people on a boat at rest in frictionless water. the group's total mass is 1326kg , and the boat's mass is 1.2×104kg . the entire party walks the 6.3m distance from bow to stern.

how far does the boat move?

In this problem, we use moment balance to get how far the boat moves. In this case, we multiply the mass of an object multiplied by the distance of the object. In this case, the balance goes: 
1326 kg * 6.5 m = 1.2 x 104 kg * x where x is the distance
x is equal to 0.71825 meters.