In a cellar there are three light switches. One of them turns on the light of the first floor. You do not know which one it is. You may go but only once in the first floor to look up. How do you find out which one of the three light switches turns on the light of the first floor?
[tab]You go downstairs and flip two switches. If lights are off, the correct one is the one you didn’t flip. If lights are on… you go to the kitchen and grab a brew and chill :p[/tab]
[tab]You turn on the first switch, leave it on and after 10 minutes you turn it off. Then you turn on the second switch and go upstairs. If the light is on, it’s the second switch. If the light is off, but the lightbulb is still warm, it’s the first switch. Else it must be the third one.
No wife required .[/tab]