Riddle: A woman is sitting in her hotel room when someone knocks at the door. She opened the door to find a man she’s never seen before. He says, "Oh I'm sorry, I made a mistake and thought this was my room." He then ran away and got into an elevator so the woman shut her door and phoned security. What made the woman so suspicious?
Answer: You don’t knock on your own hotel room door.
Riddle: There are 3 switches outside of a room, all in the off position. One of them controls a lightbulb inside the room, the other two do nothing. You cannot see into the room, and once you open the door to the room, you cannot flip any of the switches anymore. Before going into the room, how would you flip the switches in order to be able to tell which switch controls the light bulb?
Answer: lip the first switch and keep it flipped for five minutes. Then unflip it, and flip the second switch. Go into the room. If the lightbulb is off but warm, the first switch controls it. If the light is on, the second switch controls it. If the light is off and cool, the third switch controls it.