First we need to figure out how much over the limit the passengers are.
750 - 450 = 300 kg over the limit
To figure out how many people need to get off, divide 300 kg by the 70 kg weight of each passenger.
[tex] \frac{300}{70} = 4.28[/tex]
We can't remove part of a person, so round up.
The answer is 5 people.
