Fewest trips you can make

Question

It is a family day at the creek. One of the most popular activities is the canoe Relay. Each team must have two  adults and three campers. In order to win this race you must canoe all team members from one shore across the shallow river to the other shore. They must follow these rules as to who can be on a crossing: one adult; one camper; one adult and one camper; or two campers. What is the fewest trips you could make to win relay

Answer 1

There are a number of ways to reach the number 4.  But in simple terms, if 2 always go across, 1 must come back, so it must take 4 trips to get everyone over.