OT: Help me solve this puzzle

[Confused]

This is a puzzle my maths teacher told us today, but isn't telling us the answers til tomorrow, and i'd love to go in and have the answer, so here's the problem


You have an unlimited number of pieces of string, all of varying lengths, and widths. No two are identical. Each one burns for exactly 1 hour, but they do not burn uniformly.

You have an unlimited number of matches. How do you measure a time period of 15 minutes?


Can you solve this?

ConfusedBW

 

[Tarca]

Take two pieces of string.

Light both ends of one string and one end of the other string, when the first string burns up a half hour has passed, extinquish the second string.

Now light the half burnt string on both ends it already burnt for a half hour now with both ends burning it will burn out in 15 min.

 

[Fingers]

sounds good, but since they don't burn uniformly I don't think that would work.

i don't have an answer either.

A little too hard for me.

or i'm too lazy to think about it.

I like the second answer better

 

[teriba]

Tarca's works

 

[paf077]

Tarca, you're answer would be right if not for <but they do not burn uniformly.>

I am still working on it, may have an answer later!

 

[teriba]

You could say instead of extinguishing and then relighting, just wait for the first string to be done and then light the other end of the second string.

 

[teriba]

<< Tarca, you're answer would be right if not for <but they do not burn uniformly.>

I am still working on it, may have an answer later! >>



Doesn't matter. The midpoint on the first string might be shifted but it's still exactly 30 minutes. One side might burn 2cm in that 30 minutes while the other side burns 6cm.

Now imagine you had two identical strings and the second string you lit the fast burning side first. Then you will be left with a 2cm string after 30 minutes and it will take 15 minutes for it to burn completely while lit from both ends and again it might no be at the midpoint.

 

[paf077]

That wouldn't work, teriba, b/c they all burn for 1 hour!

Sorry, too late for this reply.

 

[paf077]

True, teriba, it is the correct answer!

 

[teriba]

I would bet you a lot of money on this one

 

[teriba]

<< True, teriba, it is the correct answer! >>



Doh, you agreed with me

 

[teriba]

It was Tarca's idea though.

 

[Tarca]

Thanks teriba for explaining my answer.

I love puzzles! That's why I work on computers. LOL

No day is ever the same! Always new puzzles to deal with.

 

[networkman]

Um, even with the explanation.. I still don't get it! :Q

 

[Tarca]

...............................First string.....(-------------------) second string.....{--------------}
light both ends on first string.......(--->---------<---)and 1 end on2nd {-->----------}
When first string is done burning.(-----------><----) it does not matter if it burns unevenly because we know that if we light one end it will burn for and hour, light both ends and it will only burn for 1/2 hour. Now when the first string is finished you light the other end of string 2.

Since string 1 and 2 burned for a 1/2 hour then string 2 only has a 1/2 hour of burn time left so if we light the other end that string will only burn for another 15 min.



Confused let us know what your teacher says. I'll bet money this is the route he will go.

 

[teriba]

Agreed, I'll put a little wager on this as well.

 

[Robor]

 

[PieDerro]

As far as I can tell, Tarca and Teriba look to be spot on

You guys still amaze me... damn logical thinking... never mastered it

 

[networkman]

You have an unlimited number of pieces of string, all of varying lengths, and widths. No two are identical. Each one burns for exactly 1 hour, but they do not burn uniformly.

I see conflict right here - if no two are identical and none of them burn uniformly, then it's completely IMPOSSIBLE for them each one to take exactly an hour to burn!!

BTW, I figured out that the number of matches is useless info.

Since string 1 and 2 burned for a 1/2 hour then string 2 only has a 1/2 hour of burn time left so if we light the other end that string will only burn for another 15 min.

Based on the information presented above, you cannot make such an assertion that each has burned for half an hour, because the burn rate is not uniform!

Someone has messed up the wording of the puzzle.

 

[Fingers]

now that I have more time to think about it I think you are right. Makes sense to me.

 

[MoFunk]

Damn you guys are making my brain hurt!!!!! I need to go do something a little easier, Like figure out Windows2000 Server!

 

[RaySun2Be]

As I tried to ponder the resolution of this enigma,
To provide and answer correct, and without stigma,
I remembered the veritable words of Mr. Gumby, of Bumby's Theater;

[affected british accent]My Brain Hurts![/affected british accent]

 

[ishmael2k]

Well looking at the question and taking it at its' exact wording then my answer would have to be... Look at your watch...

Doesn't say a thing about it being an all inclusive problem so bring in some outside info!


Rb

(Actually I really hate these types of puzzles and will go out of my way to avoid them...)

 

[Tarca]

Look you all. If you burn 1 string from 1 end it will burn for 1 hour, no more no less. If I light both ends of this string it does not matter if one end burns slower or not. twice the flame half the time.

What a funny thing to be discussing.LOL

 

[teriba]

Don't think distances at all. You guys are still confusing midpoints with mid-burning-points. Just think that a 1hr burntime string will burn for 1hr. If you light both ends it will burn twice as fast so it will burn for half an hour. The second string will have burnt for half an hour and then you halve that again by lighting the other side of it so it will burn for a further 15 minutes.

Don't think lengths at all.