i've seen this puzzle quite a few places see who can solve it first?
a mad bomber is out on the job, making bombs. he has two fuses (pieces of string) of varying thickness which each burn for 30 seconds. unfortunately he wants this bomb to go off in 45 seconds. he can't cut the one fuse in half because the fuses are different thicknesses and he can't be sure how long it will burn. how can he arrange the fuses to make his bomb go off at the right time?
Originally posted by kcamsTechnically, he could just cut one fuse in half. If you already know that they take 30 seconds to burn completely, half is half no matter what.
he can't cut the one fuse in half because the fuses are different thicknesses and he can't be sure how long it will burn.
Are there any other more specific clues? Like, cutting the fuses isn't an option at all? Or pre-burning the fuses isn't an option?
Don't need to cut or pre-burn.
Just lay the fuse attached to the bomb on the ground then lay the other fuse over it, perpendicular, bi-secting the second fuse. Basically creating a ' T ' with the two fuses.
Then when you light one end (a short end of the 'T'😉, it will burn half way (15 sec) and ignite the main fuse(30 sec).
Originally posted by dxzerohalf is not half no matter what, the fuses thickness varies along the length, this is what it states in the puzzle! that is what varying thickness means!
Technically, he could just cut one fuse in half. If you already know that they take 30 seconds to burn completely, half is half no matter what.
Are there any other more specific clues? Like, cutting the fuses isn't an option at all? Or pre-burning the fuses isn't an option?
the solution is he burns 1 fuse from both ends this will definitely burn for only 15seconds no matter what (though the the two ends will not reach the middle but some other point [back to the varying thickness]) then as soon as the first fuse is burned he lights the second fuse. 15 + 30 = 45.
Originally posted by Saint Nickagain this solution relies on an even thickness and equal burn which the original problem doesn't allow for.
Don't need to cut or pre-burn.
Just lay the fuse attached to the bomb on the ground then lay the other fuse over it, perpendicular, bi-secting the second fuse. Basically creating a ' T ' with the two fuses.
Then when you light one end (a short end of the 'T'😉, it will burn half way (15 sec) and ignite the main fuse(30 sec).
see previous post for ellegant solution.
Originally posted by kcamsThis is the usual answer, but how would you make it work in a bomb? Presumably the bomber wants to light the 45 sec 'fuse' and then run away.
half is not half no matter what, the fuses thickness varies along the length, this is what it states in the puzzle! that is what varying thickness means!
the solution is he burns 1 fuse from both ends this will definitely burn for only 15seconds no matter what (though the the two ends will not reach the middle but some other point [back to the varying thickness]) then as soon as the first fuse is burned he lights the second fuse. 15 + 30 = 45.
Originally posted by kcamsI think your orginal problem was not very clear.
half is not half no matter what, the fuses thickness varies along the length, this is what it states in the puzzle! that is what varying thickness means!
the solution is he burns 1 fuse from both ends this will definitely burn for only 15seconds no matter what (though the the two ends will not reach the middle but some other point [back to the varying thickness]) then as soon as the first fuse is burned he lights the second fuse. 15 + 30 = 45.
I took "varying thickness" to mean the two fuses were different thicknesses from each other. I think many others read it this way as well.
The solution you give here would not sove the problem, as the bomber would have to determine exactly where on the fuse "15 seconds" is. According to the varying thickness, he can not determine the "15 second" location on the fuse.
I think he would have to go with the pre-burning solution.
the solution is clear burning from both ends at the same time will mean that the fuse will definitely burn for only 15 seconds, the pre burning solution completly misses the point of the exercise.
it is suppose to be a simple puzzle and you've looked to deeply.
in future i'll try and be clearer in the first instance but with a riddle if it seems to obvious it probably is.
You cannot burn a varying length fuse from both ends and have it light the second fuse without human interference. How does that fufill the problem? The bomber wants the bomb to go off after 45 seconds. Under your answer he lights both ends of the first fuse waits till it is completely burnt (15 seconds) then lights the second fuse. The bomb will then go off 30 seconds later. However the bomber has to be with the bomb till after the second fuse is lit only giving him 30 seconds.
If you set the problem as measuring 45 seconds of time using the fuses then the problem makes sense.
Could the answer be to tie/splice/otherwise attach the fuses together? e.g if |--------------| is a 30second fuse, linking the two like this:
|---------------| "A"
_______|---------------| "B"
Will have "B" burning for 30 seconds, but after the first fifteen it ignites "A" that also burns for 30 seconds.
Originally posted by AThousandYoungHe only said uneven thickness, I assumed that meant just two thicknesses, e.g. on 4mm thick, one 5mm. You can't buy fuses that have widly varying thicknesses for the entire length.
The problem with that is that since the fuses are not even in thickness down their lengths, you have no way of knowing how far down the fuse is 15 seconds.
Edit - ne'er mind, I only read the original post, not the third one.