Four band members are on one side of a bridge and need to get to the other side where the stage is in 17 minutes. Only two people can cross at a time, because the bridge can’t bear the weight of any more than two people. Whenever anyone crosses the bridge they need to have a flashlight with them because it is dark. There is only one flashlight and if two people share it, they walk at the speed of the slower person. As individuals, these four people take 1, 2, 5 and 10 minutes to cross the bridge. Find a way for the four of them to get to the other side of the bridge in 17 minutes.
There are no tricks. For example, no one throws the flashlight back across the bridge or anything like that. They just walk efficiently.
1 and 2 go over. (2 minutes)
1 comes back. (3 minutes)
5 and 10 go over. (13 minutes)
2 comes back. (15 minutes)
1 and 2 go over. (17 minutes)