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Torch and Bridge Puzzle

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The Torch and Bridge Puzzle is a classic logical puzzle that goes as follows:

At night, four individuals (A, B, C, and D) need to cross a bridge. A takes 1 minute, B takes 2 minutes, C takes 5 minutes, and D takes 8 minutes to cross the bridge. They have only one torch with them, and it is necessary to carry it to cross the bridge. Only two persons can be on the bridge simultaneously, and when two individuals cross the bridge together, they must move at the pace of the slower person.

Torch and Bridge Puzzle

Torch and Bridge Puzzle Solution

To solve this problem, we can use the following strategy:

  1. A and B cross the bridge first. It will take them two minutes, as A is the faster one.
  2. A goes back with the torch (it will take him one minute).
  3. C and D cross the bridge together. As D is the slowest, it will take them 8 minutes.
  4. B goes back with the torch (it will take him 2 minutes).
  5. A and B cross the bridge again, and it will take them 2 minutes (as B is the faster one).

In total, they will spend 1 + 2 + 8 + 2 + 2 = 15 minutes to cross the bridge.

Note: that there are other possible solutions to this problem, but this is one of the quickest ones.

Here is the solution presented in tabular format:

StepPerson(s) on the bridgeTime taken
1A and B2 minutes
2A1 minute
3C and D8 minutes
4B2 minutes
5A and B2 minutes
Total15 minutes

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