## Wednesday, July 4, 2007

### Burning Rope Timer Puzzle

How to measure time using ropes!!
The puzzle asks for measuring time with the use of ropes. Its as follows

You have two identical ropes that are non-uniform in composition. You only know one useful property of the ropes i.e. "They burn completely in 1 hour."
Now you only have a lighter and those two ropes and you've got to tell when 45 minutes have elapsed.
That means you have to measure 45 minutes using those to ropes and the lighter

So work out....
Further how many ropes will be required to measure 10 minutes!!!

1. The solution has a practical flaw of having a time lag between the two parts. ;)

2. Assume no time lag is taken in account.
(Provided you are good enough to restrict it to a few seconds)
:D

3. burn first rope from 2 ends and second rope at one end. When first rope burns completely. 2nd rope ko doosre end se aag laga do.

First rope will completely burn in 30 minutes and at that time second rope would have been burnt for 30 minutes and would have only 30 minutes life left. fire it from other end. So, when it would burn completely... it would be 45 minutes + some seconds as sandeep said...

4. kocham MadziÄ™ :*October 9, 2008 at 5:29 AM

or maybe just take one of theese ropes, bend it in half, then bend it once again so you have 4 length-equal parts. Fire it from any ending and watch until fire reaches 3/4 of it's length. Meanwhile you can take the second rope and turn it back to the shop where you got it. The returned money will be enough to afford yourself a cheap- yet good enough - chineese quartz hand watch with digital display :)

5. Kocham, that is why they specifically mentioned two ropes non-uniform in composition, hence when divided (lets say cut) into 4 equal parts they will NOT burn at same pace, the only fixed property of the ropes is they burn in precisely 1 hr. you NEED both ropes and NEED to minimize the lag of noticing the first rope finishing and starting the second end of the second one.. ..

6. first burn 2 sides of rope one and a single side of rope 2. so the first rope compeletes its burning in 30 mins. and now the 2nd rope has burned 30 mins so time left for its burning is 30 mins. now burn the 2nd rope from the other side. it compeletes its burning in 15 mins. so total 45 mins.. if u have any more doubts read the question once more

7. You are mistaken. I can prove it. Write to me in PM.

8. I can suggest to visit to you a site on which there is a lot of information on this question.

9. Anonymous is right. If all we know about the ropes is that "They burn completely in 1 hour.", there is no deductive solution.