Puzzle 5: Burn the rope..


A classic puzzle involves being given 2 ropes and a lighter. The burning of one rope from end to end takes 1 hour, however the ropes do not burn in a uniform manner (ie: if you light it at one end, the first half of the rope could burn through in one minute while the second half may take 59 minutes to burn). Your goal is to measure out 15 minutes using the two ropes and the lighter.

You can assume that lighting a rope takes zero time.

Hint: You can break the rope with your bare hands..

12 comments so far

  1. Will on

    –Solution hidden–

    Author: The solution by Will is correct. It has been removed for letting other people try.

  2. Anil Kishore on

    ya.. i got it.. 🙂
    –solution hidden–
    –correct answer–
    .
    .
    Also, i have a nice puzzle to ask u guys,, how can i ask?? Do i need to send in mail r post in comments ??

  3. Fr0z3n on

    Send in a mail to me and I will put it here on your name…
    If you want to be regular in posting such puzzles and some other informative blog post then ask for being an authors of “Gurus” and we would consider your request.

  4. DarK on

    What abt this…

    using a single rope

    it takes 1hr to burn the whole rope
    rope is not burning evenly

    break the rope in 2 parts (sizes don’t matter), part A and B

    burn both the parts A and B from both sides.

    as the ropes burn unevenly, let say A is burnt, and B has still unburnt part.

    At the moment A is finished start a new fire somewhere in mid of B, thus making 2 new parts of ropes, lets say A’ and B’

    if you continue this and the rope has 4 burnings ends always.. you can measure 15 mins using a single rope (assuming burning takes 0 time)

    About the 2nd rope.. just burn it or timepass 😀

  5. Fr0z3n on

    @DarK: You answered the follow up question that I was going to ask :@

  6. Shantha on

    Going nuts guessing the answer… When will you release the solution..

  7. mandeep singh on

    send the answer

  8. Fr0z3n on

    Dark has already given a better answer.
    I would rather leave it open for readers to at least get the other solution using both the ropes.

  9. AryaBhatia on

    Light both ends of the first rope, and one end of the second. When the first rope is completely burnt: Suppose the time taken is t1
    => t1 + t1 = 60
    => t1 = 30

    At this moment light the other end of the second rope. Suppose the time taken to burn complete this part is t2.

    Now for II rope, the total time to burn the rope completely is 60min,
    =>t1 + t2 + t2 =60
    =>t2 = 15 (Ans)

  10. Sarah Mallon on

    Please send answer have attempted to find out for 9+weeks, thank u

  11. Fr0z3n on

    Arya has given the right answer which I was looking for.

  12. Francois on

    Light both ends of the first rope and only one end of the second rope.

    When the first rope stops burning, there is 30 minutes of burning left on the second one.

    Light the second end of the second rope and it will take 15 minutes to burn


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