You are given two 60 minute long fuse ropes (i.e. the kind that
you would find on the end of a bomb) and a lighter. The fuses do
not necessarily burn at a fixed rate. For example, given an 8 foot
rope, it may take 5 minutes for the first 4 feet of the fuse to
burn, while the last 4 feet could take 55 minutes to burn (a much
slower rate) (5+55=60 minutes). Using these two fuses and the
lighter, how can you determine 45 minutes? HINT: You can use the
lighter any number of times
Light the first fuse at both ends and the other fuse at one end
simultaneously. When the first fuse is burned out, you know that
exactly half an hour has passes. You also know that the second fuse
still has exactly half an hour to go before it will be burned
completely, but we won't wait for that. Now also light the other end
of the second fuse. This means that the second fuse will be burned
completely after another quarter of an hour, which adds up to
exactly 45 minutes since we started lighting the first fuse.

