An insurance salesman walks up to a house and knocks on the door. A woman answers, and he asks her how many children she has and how old they are. She says I will give you a hint. If you multiply the 3 children's ages, you get 36. He says this is not enough information. So she gives him a 2nd hint. If you add up the children's ages, the sum is the number on the house next door. He goes next door and looks at the house number and says this is still not enough information. So she says she'll give him one last hint which is that her oldest of the 3 plays piano.
Your First Choice
You are confronted by 3 doors. Behind one of them is a car, behind the two others, you will only see a goat. Now, if you correctly pick the car, you win the car ! Otherwise, if you get one of the 2 goats, you don't get the car. So, pick any door. It doesn't matter which one, but we will suppose that you picked door #2, as an example.
Should You switch?
Now, after you have picked a door and before finding out what is actually behind it, you are shown a goat behind one of the other doors. (Remember there has to be a goat in 1 of the doors that you have not picked.) Let's say you choose door #2, as shown above. For example's sake, let's say there's a goat in door 1. The question and the riddle is : should you switch the door that you picked? In other words, in this example, should you now choose door 3? Or, should you stick with your first choice (door #2)?