I was shown this puzzle recently & I found it very interesting. You're on a game show & the game show host shows you three doors. Behind two of the doors are a goat, but the third conceals a car. If you pick the door with the car, you win the car, but if you pick a door with a goat, you lose. You pick a door & the game show host then opens one of the two remaining doors, revealing a goat. He then gives you one final option, you can stick with the door you have already chosen, or you can swap to the last remaining door. What should you do?