Two coaches and two mathletes wish to cross a river. They make a raft but it will only carry the weight of 1 coach or 2 mathletes (1 coach and 1 mathlete is too much; 1 mathlete is just fine). What is the minimum number of times the raft must cross the river to get all four people to the other side? (Note: the raft can not cross the river if it’s empty - you need at least one person on it!)

First take both mathletes to the other side leaving 1 there and 1 to take the raft back, once you take the raft back have a coach take it back across and then have the mathlete that has already crossed the river take the raft back to pick up the other mathlete, have them both cross the river to the coach and leave 1 of them there, proceed to pick up the last coach and take them across the river and have the mathlete on that side bring the raft back to pick up the mathlete and cross the river.