Aug 2, 2007 -- posted by TechMonk
A classic puzzle involves being given 2 ropes and a lighter. The burning of one rope from end to end takes 1 hour, however the ropes do not burn in a uniform manner (ie: if you light it at one end, the first half of the rope could burn through in one minute while the second half may take 59 minutes to burn). Your goal is to measure out 15 minutes using the two ropes and the lighter.
You can assume that lighting a rope takes zero time.
Hint: You can break the rope with your bare hands..
Best Solution by Dark
using a single rope
it takes 1hr to burn the whole rope
rope is not burning evenly
break the rope in 2 parts (sizes don’t matter), part A and B
burn both the parts A and B from both sides.
as the ropes burn unevenly, let say A is burnt, and B has still unburnt part.
At the moment A is finished start a new fire somewhere in mid of B, thus making 2 new parts of ropes, lets say A’ and B’
if you continue this and the rope has 4 burnings ends always.. you can measure 15 mins using a single rope (assuming burning takes 0 time)
About the 2nd rope.. just burn it or timepass