Brain Teasers

You are alone and have lost all sense of time and you have no way to tell time.  You do, however, have an endless supply of fuses and matches.  Each fuse burns in its entirety in exactly 60 seconds.  However, each fuse varies in length and burns unevenly when lit from either end, i.e. the fuse does not necessarily burn half of its length in 30 seconds.  How can you make a fuse that will burn in exactly 15 seconds?

You are incredibly coordinated and it is possible to light multiple fuses simultaneously and to light a fuse on both ends at the same time.  Furthermore, you can extinguish lit fuses.

One solution is:

1. Simultaneously light a fuse, A, on both ends and another fuse, B, on one end.
   
2. When fuse A has completely burned, extinguish fuse B.  The
   remainder is a fuse that when lit from both ends will completely
   burn in 15 seconds.