In order to solve this puzzling riddle, you will have to think logically. Not everyone can figure it out. Can you?
In a house, there is a room with a light bulb inside. The door is closed, and you are outside the room. There are three switches outside the room. Only one of them operates the light bulb, while the other two do nothing. The room has no windows, and there is no way to see inside the room or tell if the light is on or off when the door is closed.
You can flip the switches as many times as you like, and there is no time limit. However, you may open the door and enter only once to check the light bulb, and you cannot flip the switches while the door is open.
Your challenge is this: Can you figure out which switch operates the light bulb in the room?
This may seem impossible, but there is a way to logically find out the answer. Take a moment to think about it, and when you think you know, or if you've racked your brain but to no avail, scroll down to see the answer.
Were you able to figure it out?
You must use logic, as well as efficiency and common sense. As you can only open the door once, you have to make every move count. And it's not all academic, for you will need your sense of feel to solve this.
Here is the solution:
First, turn on two of the three switches and wait a few minutes. Five or ten minutes will do.
Next, turn off one of the two switches that was on and open the door. If the light is on, then you know the correct switch is the one that is still on!
However, if the light is off (and here's where your sense of feel comes into play), immediately enter the room and touch the light bulb with your hand.
If the light bulb feels warm or hot, then you know the other switch previously in the on position is the right one!
Because you left the switch on for five or ten minutes, the bulb became hot. Although you turned it off, you could still feel the heat with your hand, and so you can determine which switch was the right one!