Tuesday, October 26, 2010

The Burning Rope - One puzzle a day - Puzzle Buddies

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?

Note: Don't forget to visit us again. Answer to the puzzle will be posted tomorrow.
Solution:

If you light both ends of one rope, it will burn in exactly a 1/2 hour. Thus, burn one rope from both ends and the other rope from only one end. Once the one rope (which is burning from both ends) finally burns out (and you know a 1/2 hour has elapsed), you also know that the other rope (which is buring from only one end) has exactly 1/2 hour left to burn. Since you only want 45 minutes, light the second end of the rope. This remaining piece will burn in 15 minutes. Thus, totaling 45 minutes.
Winner: Gaurave Sehgal

1 comment:

  1. 1. Start burning one rope from both ends and other one from one end.
    2.When first one finishes that means 30 minutes have passed.
    3. Now light the other rope's other end also. Second rope will finish in 15 minutes.

    So the time taken in total 30 + 15 = 45.

    ReplyDelete