Question : You have in your possession two fuses; the classic burning kind used for detonating dynamite, and also a box of matches.
Each fuse burns for exactly one hour but the burning process is completely erratic making it impossible to determine how much time is left simply by looking at the fuse.
Your task is to time exactly forty five minutes.
How do you do it?
Answer :
Ignite one of the fuses at both ends. At the same time ignite the other fuse at one end only.
When the first fuse burns out ignite the other end of the second fuse.
When the second fuse burns out forty five minutes has elapsed.