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Burning Rope Puzzle

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  • 26-07-2009 6:33pm
    #1
    Hagar
    Closed Accounts Posts: 16,793 ✭✭✭✭


    I've searched the forum and not found this puzzle here before, apologies if I've missed it.

    The Puzzle:

    There are two lengths of rope.
    Each one can burn in exactly one hour.
    They are not necessarily of the same length or width as each other.
    They also are not of uniform width (may be wider in middle than on the end), thus burning half of the rope is not necessarily 1/2 hour.
    By burning the ropes, how do you measure exactly 45 minutes worth of time?


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    #2
    Thomas_S_Hunterson
    Closed Accounts Posts: 6,151 ✭✭✭Thomas_S_Hunterson


    Ok at t=0, light one rope at both ends and the other one at one end

    The first rope will burn out in exactly 30 mins, at which time you light the other end of the other rope. The remainder of this rope will burn out in a further 15 mins.


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    #3
    Hagar
    Closed Accounts Posts: 16,793 ✭✭✭✭Hagar


    Very quick off the mark there, well done.


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    #4
    orourkeda
    Closed Accounts Posts: 17,918 ✭✭✭✭orourkeda


    .


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    #5
    FruitLover
    Registered Users Posts: 2,534 ✭✭✭FruitLover


    Hagar wrote: »
    By burning the ropes, how do you measure exactly 45 minutes worth of time?

    Set off a stopwatch as you begin to burn the ropes.


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