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Brainteaser #17- Bridge & Torch Problem -

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Puzzle Image It's late at night when four travelers come upon a narrow bridge that they need to cross. It's very dark so they need to use a torch to cross the bridge safely. It's an old wooden bridge and a sign reads "Warning: No more than two people on the bridge at a time". They have a single torch between them which lasts 15 minutes once lit. Each of the four travelers (A, B, C, and D) requires a different amount of time to cross the bridge. A: one minute, B: two minutes, C: five minutes, and D: eight minutes. Given the two-person bridge limit, how can the entire group get to the other side of the bridge before the torch burns out (i.e. in 15 minutes)?

You can use the table below to enter the details of each crossing:

Elapsed Time Starting Side Action Ending Side
0 minutes A B C D    
Do you have a suggestion for this puzzle (e.g. something that should be mentioned/clarified in the question or solution, bug, typo, etc.)?