Aug 2, 2007 -- posted by TechMonk

## Puzzle 5: Burn the rope..

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

Light both ends of the first rope and only one end of the second rope.

When the first rope stops burning, there is 30 minutes of burning left on the second one.

Light the second end of the second rope and it will take 15 minutes to burn

Arya has given the right answer which I was looking for.

Please send answer have attempted to find out for 9+weeks, thank u

Light both ends of the first rope, and one end of the second. When the first rope is completely burnt: Suppose the time taken is t1

=> t1 + t1 = 60

=> t1 = 30

At this moment light the other end of the second rope. Suppose the time taken to burn complete this part is t2.

Now for II rope, the total time to burn the rope completely is 60min,

=>t1 + t2 + t2 =60

=>t2 = 15 (Ans)

Dark has already given a better answer.

I would rather leave it open for readers to at least get the other solution using both the ropes.

send the answer

Going nuts guessing the answer… When will you release the solution..

@DarK: You answered the follow up question that I was going to ask :@

What abt this…

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 😀

Send in a mail to me and I will put it here on your name…

If you want to be regular in posting such puzzles and some other informative blog post then ask for being an authors of “Gurus” and we would consider your request.

ya.. i got it.. 🙂

–solution hidden–

–correct answer–

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Also, i have a nice puzzle to ask u guys,, how can i ask?? Do i need to send in mail r post in comments ??

–Solution hidden–

Author: The solution by Will is correct. It has been removed for letting other people try.

i need answer how to get?

Look at DaKs’s answer