viernes, 18 de febrero de 2011


Inside a hermetically sealed room there is a light bulb, and outside the room there are three switches. Only one of the three lights the bulb. While the door is closed, you can press the switches as often as you want. But when you open the door, you have to say which of the 3 switches lights the bulb.

2 comentarios:

  1. This puzzle appears in the movie "Fermat's room".I remember that to resolve it you should check the temperature of the bulb, if the bulb was hot, the last switch was powered lighting the lamp. You are doing a great job on this blog. A greeting from the administration of the blog "2matehumanes"