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Math Help - four men puzzle

  1. #1
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    Red face four men puzzle

    4 men have to cross a deep ravine at night. There is a bridge across, but it is old and can only supportr the weight of 2 men at a time. they have 1 flashlight among them, which they need to see their way across, if two men cross at the same time, they must travel at the pace of the slower man. Th fastest man takes 1 minute to cross, the next fastest two minutes,the third 5 minutes, and the slowest 10 minutes.
    What is the shortest amount of time it can take them to cross? Don't forget that the men need the flashlight to see their way across, so someone must bring it back if there are still people left to cross the bridge.

    i keep getting 23... is that right?
    Last edited by annie3993; May 25th 2008 at 02:11 PM.
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  2. #2
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    Quote Originally Posted by annie3993 View Post
    4 men have to cross a deep ravine at night. There is a bridge across, but it is old and can only supportr the weight of 2 men at a time. they have 1 flashlight among them, which they need to see their way across, if two men cross at the same time, they must travel at the pace of the slower man. Th fastest man takes 1 minute to cross, the next fastest two minutes,the third 5 minutes, and the slowest 10 minutes.
    What is the shortest amount of time it can take them to cross? Don't forget that the men need the flashlight to see their way across, so someone must bring it back if there are still people left to cross the bridge.

    i keep getting 23... is that right?
    Well you want the fastest man moving the flashlight...

    Him and the next fastest cross taking 2 minutes

    He then walks back adding a minute

    Then him and the next take 5 minutes

    He walks back adding a minute

    Then him and the next cross adding 10

    2 + 1 + 5 + 1 + 10 = 19 minutes
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