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Light a fuse

Logic puzzles require you to think. You will have to be logical in your reasoning.


Puzzle ID:#697
Fun:*** (2.42)
Difficulty:*** (2.57)
Submitted By:link2440**
Corrected By:sdm1177




You have 2 fuses. One fuse burns for 1 hour, the other burns for 2 hours. The problem is that the fuses burn irregular. The last few inches may burn longer than first few inches. Using the 2 fuses how can you create a fuse that burns for exactly 45 minutes. Remember, cutting them does no good since you don't know how long the cut fuse lasts.


You burn both sides of the 1 hour fuse and 1 side of the 2 hour fuse at the same time. Regardless of the varying speeds of the one hour fuse, when it goes out it has been 30 minutes. At that point there would be 1 hour and 30 minutes left on the 2 hour fuse. You then light the other end of the 2 hour fuse and since the burning time would be cut in half the fuse would be 45 minutes long.

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(user deleted)
Nov 16, 2001

An excelent puzzle, but you don't really come out of it with a fuse that you could use.

It would not be possible to use the result to set a 45 second burn to, for example, ignite a firework
Oct 22, 2006

45 minutes, not 45 seconds!
Feb 17, 2012

Echo first comment - the solution does not satisfy the requirement to create a usable 45 minute fuse. If you start instead with both a 30 minute and a 60 minute fuse, then you can burn both ends of the 30 and one end of the 60, put out the 60 at 15 (when the 30 goes out) and you then have a usable 45 minute fuse.
Nov 11, 2013

but there is no requirement to create a usable fuse

the requirement of this puzzle is just to be able to measure time -> 45 minutes

don't have a cow man

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