Brain Teasers · The Burning Ropes
Burning Rope Puzzle - Measure 45 Minutes, Played
Two ropes that each burn for an hour, unevenly, and a lighter: time exactly 45 minutes.
What is the burning rope puzzle?
Each rope burns for exactly 60 minutes but unevenly, so its length tells you nothing about time. What you can control is how many flames are burning it.
Lighting both ends halves whatever burning time is left. With two ropes, that one move gives you 30, 15 and 45 minutes.
How it works
Two ropes that each take 60 minutes to burn end to end, but unevenly, and a lighter. The story asks how to time exactly 45 minutes. You pick one of four answers. Then you step through the answer and the breakdown.
How scoring works
This teaser checks your answer. A wrong pick is crossed out. You get two tries before the answer opens. A correct first try earns a ticket; a second try or opening the answer early is recorded but earns nothing. The story teasers share one lifetime unlock for free users.
The key insight
Light rope A at both ends and rope B at one end. A burns out at 30 minutes. Light B's other end then: its last 30 minutes of burning take 15. When B goes out, 45 minutes have passed.
The full step-by-step solution lives at /brain-teasers/burning-ropes/solution.
A worked example
Time 0: A lit at both ends, B at one end. Time 30: A is gone, B has 30 minutes left, light its other end. Time 45: B is gone.
Common mistakes
• Cutting or marking a rope at its halfway point - uneven burning makes that meaningless.
• Lighting both ropes at both ends, which only times 30 minutes.
• Forgetting that rope B must be burning from the start.
Why interviews test this
Interviewers want you to rule out length straight away and state the both-ends fact before using it. The written solution is at /brain-teasers/burning-ropes/solution.
Play The Burning Ropes on Outcry
The Burning Ropes is free to play on Outcry, in the Brain Teasers section, and every run is timed and scored. Read the guide once, then play The Burning Ropes and check your score against the strategy above. The guide book has a written guide for every other game, and the practice hub and mock assessments put the same skills under a real screen's clock.