Crossing bridge in 15 minutes! Come on Fast!!!!


Four people arrive at a river with a narrow bridge that can only hold two people at a time. It’s nighttime and they have one torch that has to be used when crossing the bridge. Person A can cross the bridge in one minute, B in two minutes, C in five minutes, and D in eight minutes. When two people cross the bridge together, they must move at the slower person’s pace.

Can they all get across the bridge in 15 minutes or less?

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    Best answer

    Consider first A & B cross the bridge. A returns with the torch.
    Time taken is 2 + 1 = 3 minutes

    Then C & D cross the bridge. However, B returns with the torch.
    Time taken is 8 + 2 = 10 minutes.

    Now, both A & B cross the bridge.
    Time taken is 2 minutes.

    Total time taken: 3 + 10 + 2 = 15 minutes.

    bhola99 Expert Answered on 20th February 2020.
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