Overview
The burning-rope puzzle breaks a stubborn assumption: that a rope burning for 60 minutes reaches its halfway point at 30. Since it burns unevenly, you must measure time differently.
How to solve The Burning Ropes
- Light rope A at both ends and rope B at one end simultaneously.
- Two flames consume rope A in 30 minutes regardless of shape.
- At that moment light B's second end; its remaining 30 minutes of rope now burns in 15 — total 45.
The key insight
Burning from both ends always halves the remaining time, whatever the rope's shape. That turns an unmeasurable rope into a reliable clock.
Variations & echoes
- With more ropes you can measure 15, 22.5, and other fractions by combining both-end lights.
- It teaches thinking in rates of consumption, not lengths.
Frequently asked questions
Can I measure 15 minutes?
Yes: after the 45-minute method, the same both-ends trick on a fresh rope started at 30 minutes isolates a 15-minute span.