Given 2 fuses, each can be burned in exactly 1 hour. However, both fuses are not uniform and we have no clue which part burns faster and which slower.
Question: how to measure 45 minutes using these 2 fuses?
Answer:
First measure 30 min, and then measure 15 min.
How to measure 30 min? Light a fuse from both ends at the time.
How to measure 15 min? That's half of 30 min. So light a fuse from both ends after it has burned 30 min.
Final answer is:
1. First light 2 ends of one fuse and 1 end of the other fuse at the same time (time 0 now);
2. At the time one fuse is burned up, light the other end of the remaining fuse (30 min now);
3. When the second fuse is burned up, it's 45 min.
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