here's a puzzler

you have unlimited number of small pieces of string of any material you like... each and every one of them is of varying length and density so that no piece of string has its match...

the only thing that they have in common is that each and every one of them burn from end to end in exactly one hour...

you are alone in a room with all these strings and a lighter and nothing else...

all you need to do is manage to count one hour and a half... (no, you don't have watch or clock )


well???

P.S. for those of you who already know the answer please don't give it away...

P.S. 2 i didn't find it until they told me...

P.S. 3 there's no trick whatsoever, the answer is pretty logical...

P.S 4 probably the dumbest and shortest thread but i'm really bored so....

I'm not sure you could tie a knot exactly in the middle of the string, or at least I know I wouldn't be able to.  I think that would give you a good approximation of an hour and a half if you're accurate enough, but it wouldn't be exact.

I think a better option would be to set the first on fire, and then find a long and thin piece of string.  Loop that piece of string around so that its two ends touch, and then place that next to the unlit end of the string that's on fire.  Then once the first string burns for an hour, the second string would catch fire on both ends, so once it finishes burning an hour and a half would have elapsed since the first was set on fire.

Rubidium wrote: I'm not sure you could tie a knot exactly in the middle of the string, or at least I know I wouldn't be able to.  I think that would give you a good approximation of an hour and a half if you're accurate enough, but it wouldn't be exact.I think a better option would be to set the first on fire, and then find a long and thin piece of string.  Loop that piece of string around so that its two ends touch, and then place that next to the unlit end of the string that's on fire.  Then once the first string burns for an hour, the second string would catch fire on both ends, so once it finishes burning an hour and a half would have elapsed since the first was set on fire.

    
you're right my friend... all you have to do is burn any string simultaneously from both ends...

good job