# Probability Line

Probability is the**chance**that something will happen. It can be shown on a line:

The probability of an event occurring is somewhere between impossible and certain.

As well as words, we can use numbers to show the probability of something happening:

- Impossible is
**zero** - Certain is
**one**

We can use fractions:

Or percents:

Or decimals:

### Example: here we show the probability that:

**a)**The sun will rise tomorrow**b)**I will not have to learn mathematics at school**c)**If I flip a coin it will land heads up**d)**Choosing a red ball from a bag with 1 red ball and 3 green balls

Where would you place names like "fair chance", "remote chance", "possible", "probable" and "improbable"?

## Between 0 and 1

- The probability of an event will
**not**be less than 0.

This is because 0 is impossible (sure that something will not happen). - The probability of an event will
**not**be more than 1.

This is because 1 is certain that something will happen.

## Names

People use many names when talking about probability! Such as odds, chance and so on.

### Example: 50/50 chance

means exactly **50%** chance, which is also **0.5** or **½**

## Notation

In mathematics we use the letter **P** to mean "probability of", like this:

### Example: "the probability of choosing an ace is 1 in 13" is written:

P(ace) = \frac{1}{13}

It sure saves a lot of writing!