Video: Determining the Probability of an Event in a Dice Experiment

Kathryn Kingham

What is the probability of rolling a number greater than or equal to 2 on a regular die?

02:22

Video Transcript

What is the probability of rolling a number greater than or equal to two on a regular die?

First, we remember the probability of an event is equal to the number of ways the event can occur over the total possible outcomes. Our event is rolling a number greater than or equal to two. We want to show the number of ways to roll a number greater than or equal to two over all possible numbers rolled.

If you think about a regular die, we know that it’s a cube made of six faces. And the faces are numbered one, two, three, four, five, six. Thinking about our event, we need to determine how many of these faces are greater than or equal to two. Two is greater than or equal to two. Three is greater than two. Four is greater than two. Five is greater than two and so is six.

We have five outcomes greater than or equal to two. The numerator for our probability — the number of ways to roll a number greater than or equal to two — is five. What would be the denominator? How many possible outcomes are there? How many different numbers could be rolled? Because the die has six faces, there are six possible outcomes. Our denominator equals six.

The probability of rolling a number greater than or equal to two on a regular die is five out of six, five-sixths.

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