In 45 minutes...

You're trapped in a room with nothing except one match, and three identical ropes in it. Let's say that you want to know when 45 minutes has passed so you can call your non-existent girlfriend on your non-existent phone. For the point of the puzzle, we're also going to assume that you're incapable of counting the time yourself, that you're wearing a balerina costume, and are a raging alcoholic just for fun.

So anyway, the only knowledge that you posess of the ropes is that it always takes 30 minutes to burn one. But you don't know if the ropes will burn at an even rate. How do you determine when 45 minutes has passed?

Originally posted by ark13
You're trapped in a room with nothing except one match, and three identical ropes in it. Let's say that you want to know when 45 minutes has passed so you can call your non-existent girlfriend on your non-existent phone. For the point of the puzzle, we're also going to assume that you're incapable of counting the time yourself, that you're wearing a bal ...[text shortened]... t know if the ropes will burn at an even rate. How do you determine when 45 minutes has passed?

Originally posted by Mephisto2
burn a rope for the first half hour, near the end, use the flame to lit a second one to be used as a match. When the first rope is burnt up, lit the third rope on both sides. That rope will burn for 15 minutes, and then the 45 minutes are over ?

Well there is a simple way actually. You light both of their ends...
EDIT: Argh, Mephisto was again first, and mine was messed up anyway 🙁

Originally posted by ark13
Yup, that was fast.🙂

Originally posted by XanthosNZ
There was a very long thread on this (and the ambiguous wording that it contained) a couple of months back.