Cook the egg for 15 minutes

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You are trying to cook an egg for exactly fifteen minutes, but instead of a timer, you are given two ropes which burn for exactly 1 hour each. The ropes, however, are of uneven densities – i e , half the rope length-wise might take only two minutes to burn. How can you cook the egg for exactly fifteen minutes?

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    We light rope A from one end and rope B from both ends simultaneously.
    When rope B is fully burned (it means that half an hour is passed and rope A has only one hour left) we light the other end of rope A immediately and of course start cooking the egg.
    When rope A is fully burned (it means that fifteen minutes is passed from the time we started cooking the egg) your meal is ready…! 😉

    Detective Expert Answered on 18th July 2015.
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    Steps to measure 15 minutes

    1. Light Rope #1 from both ends.
    2. At the same time light Rope #2 from one end.
    3. When Rope #1 burns fully, it will be 30 minutes and Rope #2 will take 30 more minutes to burn, light the other end of Rope #2 at this time, thus it will take 15 minutes to burn.
    4. Start cooking your egg at the same point.
    5. Stop cooking when Rope #2 burns fully.
    Hacker Guru Answered on 18th July 2015.
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