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Interview Brain Teasers Medium 1 min

An interviewer gives you two ropes. Each rope takes exactly one hour to burn, but they do not burn at a uniform rate. How can you measure exactly 30 minutes?

Hint
Burn from both ends.

Answer

Light one rope at both ends.

Explanation

If a rope takes exactly one hour to burn from one end, burning it simultaneously from both ends makes it finish in exactly 30 minutes, regardless of its non-uniform burning rate.

Step-by-Step Solution

Light both ends of one rope simultaneously.
When the rope is completely burned, exactly 30 minutes have passed.
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