An example: We have two ropes. Once ignited, each rope burns exactly 1 hour. The burning process, however, is not even. It may be that almost the whole rope is set afire in a second and the other small bit of it is moldering for the rest 59 mins 59 seconds. The idea is we don't know how long it takes for any part of the rope to burn down. The task is, using these two ropes and fire (matches, a ligher or whatever springs to mind) measure exactly 45 minutes. We don't have watches or whatever workaround you can come up with. Just 2 one-hour ropes that can be set aflame.
