Subtle Coolness · chrono index · alpha index

Riddle 8: Burning Rope

by William Jackson on 2009-10-26

Hey, remember that time I put a bunch of riddles on my blog and solicited answers from my readers? Letʼs do that again. Refresh your knowledge of the rules, then take a crack at this conundrum.

Consider a certain kind of rope with the following characteristics: If you light one end, it will burn up in exactly one hour. Unfortunately, the rate of burning may vary unpredictably. For instance, the first half of the rope may burn in ten minutes and the second half in fifty; or it may be divided into many different areas. There is no way to tell.

Given two of these ropes (and a source of fire, of course), how do you measure 45 minutes?

Get the solution here.