If You Can Solve This Riddle, Call Mensa Immediately
By Dave Basner
February 13, 2021
If you think you are smart, there is nothing like a good riddle to prove yourself right or wrong and this brain teaser is just the one to do it. The answer isn't too tricky, but only the smartest and most creative thinkers will come up with it. In fact, Google is rumored to use it in interviews to find candidates who are strong problem solvers.
You are standing alone outside of a windowless, closed room, in front of three light switches. Each switch controls a different light in the room, but since you can't see in, you don't know which switch controls which light - you only know that each switch turns on only one light.
There are no dimmer switches and you can't touch the switches again once you open the door to the room, so how can you know which switch controls which light when you go in the room?
If you're trying to think of some loophole, you don't need one - the answer is easier than that. Ready to hear it? Scroll down...
All you need to do is turn on two of the lights, wait a couple minutes and then turn one of the two off. When you go in the room, the light that's on is obviously controlled by the switch in the on position. As for the two that are off, if you touch the light bulbs, the warm one is connected to the switch that was on and then turned off, and the cold bulb is controlled by the switch you never turned on.
So would you get hired at Google?
Photo: Getty Images