The Flashlight Puzzle (& More)

The Puzzle

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. There is 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.

Each man walks at a different speed. A pair must walk together at a rate of the slower man's pace.

Man 1: 1 minute to cross.
Man 2: 2 minutes to cross.
Man 3: 5 minutes to cross.
Man 4: 10 minutes to cross.

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.

To Tricky?

When I first saw this, I thought is was impossible, as:

Even if the fastest man travels over with a slower one (1 & 4 - 10 minutes) and returns (11 minutes) by the time he takes another (1 & 3 - 16 minutes) and returns for the second quickest man, time is up.

Very tricky... but it is possible.

Make sure you've really got it before looking here.

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