Monday, 17 July 2017

Puzzle | Rope burning puzzle


You have two ropes and a lighter. Each rope has the following property: If you light one end of the rope, it will take one hour to burn to the other end. They don't necessarily burn at a uniform rate. How can you measure a period of 45 minutes?

Hint:
Both the ropes take longer than 45 minutes to burn from one end to other. So we need to speed up the process to measure the 45 minutes.

Solution:

Light both ends of rope A and one end of rope B. After 30 minutes, rope A will be completely burned up and there will be 30 minutes of rope B left. Light the other end of rope B; it will burn up in 15 minutes. Total time elapsed since starting the ropes on fire: 45 minutes.

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