This question already has an answer here:
- Burning ropes as timers 5 answers
You have 2 safety fuses and 4 matches. Each fuse takes exactly one hour to burn, but they are not perfect so may not necessarily burn evenly from both sides. For example, the first half might burn in 20 minutes and the second half might take 40 mins. but this does not change the total time to be burnt as stated.
How can you measure out 45 minutes by just using these two safety fuses and the matches you have?