Bridge Crossing Puzzle

Four people need to move from one side of a bridge to the other at night.

Each can cross at different speeds: 1, 2, 5, and 10 min.

There is only one flashlight and it must be carried each time someone crosses the bridge.

The bridge will only support two people at a time.

Two crossing together move at the slower speed of the two.

You cannot throw it across to your friends on the other side.

What is the shortest time required to get all 4 to the other side?

How quick across?

How quick across?



Obvious answer: Have fastest escort others takes 19 min.

17 min solution: 1 escorts 2 and returns, 5 escorts 10 and 2 returns, and 1 escorts 2 to complete.

17 minute solution

17 minute solution

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