There are 4 men who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night time, and there is only one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. The parties cannot split up on the bridge - the flashlight must be with each person who is on the bridge. Each man walks at a different speed. A pair must walk together at the rate of the slower mans pace. For example if Man 1 and Man 4 walk across first. 10 Minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight, a total of 20 minutes have passed and you have failed the mission.

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