Here's a somewhat difficult riddle for you guys (and gals)

[blahblah99]

There are two uneven ropes that will take exactly an hour to burn each. These two ropes have different length. Now using these two ropes, you need to measure 45 minutes. You cannot assume that folding or burning half of a rope is 30 minutes since it is uneven, for example, it might take 30 minutes to burn 15% of one rope. How can you measure 45 minutes by using only these two ropes and a box of matches?



if you know the answer, please don't spoil it for others!

 

[dionx]

thats easy

 

[dude]

Stopwatch.

 

[Rage187]

tie both ropes together

 

[need4spd]

oh.. I have the answer. But don't wanna ruin the riddle for others :disgust::Q

 

[Atlantean]

ok then I won't spoil it.

 

[DanFungus]

<< if you know the answer, please don't spoil it for others! >>


I have NO objection if you do spoil it for me I'm just dumb, or something.....numbed after 3 hours of homework I just finished....I hate Emily Dickenson...

 

[TallBill]

hehe, nm.. i got the answer

 

[b0mbrman]

got it

 

[MaxDSP]

PM me da answer

 

[BruinEd03]

<< There are two uneven ropes that will take exactly an hour to burn each. These two ropes have different length. Now using these two ropes, you need to measure 45 minutes. You cannot assume that folding or burning half of a rope is 30 minutes since it is uneven, for example, it might take 30 minutes to burn 15% of one rope. How can you measure 45 minutes by using only these two ropes and a box of matches?



if you know the answer, please don't spoil it for others! >>



So you're telling me the material is not consistent throughout rope A or rope B? that say it takes the first 30 mins to burn 15% of ropeA ...then it takes 30 mins to burn the rest of the 85%?

-Ed

 

[TallBill]

hes saying the burn rate is not consistant or known

 

[notfred]

Just post the answer.

 

[TallBill]

i can get 30 minutes time.... if you light both ends of one rope... no matter what the burn rate.. it'll be done in 30 minutes.. i have no clue how to get the 15

 

[Razorwyre]

Light one rope at both ends=30 minutes
After that, light the other rope in the middle, and at both ends=15 minutes

30+15= 45minutes

 

[DuffmanOhYeah]

<< Light one rope at both ends=30 minutes
After that, light the other rope in the middle, and at both ends=15 minutes

30+15= 45minutes >>


Maybe its the almost 45 hours without sleep, but that doesn't work at all...........

 

[polypterus]

<< Light one rope at both ends=30 minutes
After that, light the other rope in the middle, and at both ends=15 minutes

30+15= 45minutes >>



But if the burn rate wasn't consistent isn't it possible that the two pieces of the second rope would finish at different times? Otherwise you could just light the first rope in the middle.

dc

 

[b0mbrman]

Otherwise you could just light the first rope in the middle.

Yawp...or at the 3/4 point

 

[Gonad the Barbarian]

<< Light one rope at both ends=30 minutes
After that, light the other rope in the middle, and at both ends=15 minutes

30+15= 45minutes >>



Is that supposed to be the answer? That won't work if the ropes are suspended vertically.

 

[johnjbruin]

I know the answer.
Just wondering if you are in any way related to the interview for HKN at UCLA. If you have no idea of wth i am talking about, then forget it.

 

[S0me1X]

The method to get 15 minutes does not exactly work:

Lets say that the rope looks something like this:
<> <> <> <> <> [] [] [] [] [] [] [] [] [] [] [] [] [] [] []
Physically, the segments are of equal length.
The time it takes to burn a <> segment is 6 minutes, the time it takes to burn a [] segment is 2 minutes. Total time = 6x5 + 2x15 = 60 minutes

Now, if you were to start burning the rope from either end, it would take 60 minutes to burn the entire rope.

If you were to start at both ends, it would take 30 minutes to burn the entire rope (so good so far).

But if you were to start at the middle and both ends:
15 minutes later, the left end would not have finished burning, whereas the right end would have burned out before 15 minutes was up.

To check this: the left side has 6x5 + 2x5 = 40 minutes of 'burn time'
the right side has 2x10 = 20 minutes of burn time.

<> <> <> <> <> [] [] [] [] [] middle [] [] [] [] [] [] [] [] [] []

 

[Gonad the Barbarian]

What is the answer? Count to sixty 45 times?

 

[S0me1X]

PM me if that logic was wrong.

 

[Gonad the Barbarian]

I have it. If you intertwine them you have one rope that completely burns in one and a half hours. Then light both ends of that rope and it cuts the burn time in half to 45 min.

But then again, this still won't work if the ropes are suspended vertically. I assume they are not?

Nevermind, I thought one of the ropes burned in 30 minutes. Somebody post the g0dd@mn answer.

 

[S0me1X]

what do you mean, intertwine them cuts burn time to 1 hour 30 minutes? They are of different length right?