Skill: Write probability as a decimal

A probability can be written as a decimal by dividing:

$$\text{probability}=\frac{\text{number of favorable outcomes}}{\text{total number of equally likely outcomes}}$$

The favorable outcomes are the outcomes you want. The total outcomes are all possible outcomes.

Example: What is the probability of rolling an even number on a fair six-sided die?

1. List the possible outcomes: $1,2,3,4,5,6$. There are $6$ total outcomes.

2. Find the favorable outcomes. The even numbers are $2,4,6$, so there are $3$ favorable outcomes.

3. Write the probability as a fraction:

$$\frac{3}{6}$$

4. Divide the numerator by the denominator:

$$3\div 6=0.5$$

So, the probability of rolling an even number is:

$$\boxed{0.5}$$

A probability is always between $0$ and $1$. A probability of $0$ means an event is impossible, while a probability of $1$ means it is certain.