MediumBrain Teasers

Burning Ropes — 45 Minutes

Goldman SachsMorgan Stanley

You have two ropes; each takes exactly 60 minutes to burn end-to-end, but neither burns at a uniform rate. With only a lighter, how do you measure exactly 45 minutes?

Hints

Burning a rope from both ends halves its time — regardless of unevenness.

Use the moment the first rope finishes as a trigger.

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