# Factorials

If I said “**3!**“, would you think the 3 is really excited, or that you have to shout the number?

In fact, it’s a mathematical operation called *factorials*, and boy are they fun! They may seem complicated at first, but they’re really a very basic concept. The exclamation point behind a number means that you multiply that number by each successively lower number, in order, until you get to one.

So 3! would be 3 x 2 x 1 = 6.

Take a look at the video for an explanation of how factorials work and how they can be used.

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# Probability

In math, probability is how likely it is that something will occur (or not). Probability is expressed from a range from 0 to 1. A probability of zero means that a thing will definitely not happen – it’s impossible. But a probability of one means that it definitely will happen – it’s certain. Any number larger than 0, but smaller than 1 means that a thing might happen. The number 1/2, or one half, is right in the middle and it means there is a 50/50 chance. Do you think there’s a greater chance for a person to get struck by lightning, or to be hit by a meteorite?

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# Three Doors

Imagine that you are on a game show with a chance to win a car. There are three doors and the car is behind one of them. You just have to choose the correct door! You can use probability to get an possible advantage in choosing the correct door. Watch the video, and I will explain how it works.

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