Probability measures the chances that a certain event occurring. You calculate probability based on the number of successful outcomes divided by the total number of outcomes that can occur. Using a calculator makes the scientific calculations even easier. For example, when playing poker, you calculate the probability of making a hand, such as a straight or flush. Knowing the probability helps you decide whether to call a bet because you have a good chance of making your hand or fold because the probability is low.

### Step 1

Enter the number of successful outcomes. For example, if you have 25 balls in a bag, 5 of which are red, and you want to pick out a red ball, enter "5" as the number of possible successful outcomes.

### Step 2

Push the division sign.

### Step 3

Enter the total possible outcomes. For this example, since you could pull out any one of 25 balls, enter "25."

### Step 4

Push the equals sign to see the probability expressed as a decimal. In this example, you would see the probability of pulling one of 5 red balls from a bag with 25 balls, equals 0.2, or 20 percent.