Some mathematical puzzles are delightful. When we discover the principle behind them, they seem so easy ... but they may have had us 'stumped' for hours or days before gaining the insight to solve them!

This is one of those puzzles.

Once I have explained this particular puzzle to you, please pause the video and see if you can work out the solution by yourself. I know the temptation is great to view the answer right away, but you will enjoy the process much more if you 'have a go' first.

You are shown three light switches and told that only one of them controls a light in a distant room (which you cannot observe). You are allowed to manipulate the switches and then you are allowed just one visit to the room to observe the light. You are then required to identify the switch that controls the light!

By the way, when you manipulate the switches, you are not allowed to pull them apart or tamper with the wiring. You are only allowed to turn them off and/or on.

This wonderful puzzle illustrates a mathematical principle very clearly. Please watch the video to learn what it is ... and then try the puzzle on your friends and let me know how you fare.