Unrelated to three dog night :)
The other day I asked: "Imagine that you're making a magic potion. You're a wizard with a long beard. But - the potion only works if you wait exactly 45 minutes before you stir it. If you stir it before or after the potion's totally ruined. You don't have a smartphone. You don't have a watch. You don't have any kind of time measuring device. What you have is two fuses of irregular consistency. The one thing you know for a fact is that it takes an hour for each of these fuses to burn from one end to the other. How do you use these to measure exactly 45 minutes?"