Logical Puzzles Medium 4 min

You have two ropes. Each rope takes exactly 60 minutes to burn completely, but neither rope burns at a uniform rate. How can you measure exactly 45 minutes?

Hint

Lighting both ends changes the total burning time.

Answer

Light both ends of Rope A and one end of Rope B. Rope A burns out in 30 minutes. Then light the second end of Rope B. It will burn out 15 minutes later, giving exactly 45 minutes.

Explanation

Burning a rope from both ends makes its total burning time 30 minutes even when the burn rate is uneven.

Step-by-Step Solution

1. Light both ends of Rope A.
2. Light one end of Rope B.
3. When Rope A finishes, 30 minutes have passed.
4. Immediately light the other end of Rope B.
5. The remaining part of Rope B now burns from both ends and takes 15 minutes.
6. Total = 45 minutes.

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