Beside a closed door to a room there are three light switches. Only one switch is for the light inside the room. You must find the correct switch to turn on the light before you enter the room. You can enter the room only once. All three switches can be in the up or down position for the light inside the room to come on. How can you tell if you have the right switch on for the light before entering the room?
Walk in Peace and Harmony. Phyllis Doyle Burns Avatar: Fair Helena by Rackham, Public Domain