# Video: Determining the Theoretical Probability of an Event

Each section on this spinner is equally likely to be chosen. What is the probability of the arrow landing on the number 4? Give your answer as a fraction in the simplest form.

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### Video Transcript

Each section on this spinner is equally likely to be chosen. What is the probability of the arrow landing on a number four? Give your answer as a fraction in the simplest form.

When we talk about the probability of something, we’re talking about the chance of something happening. And here, we are asked to give this as a fraction. The chance of us pointing to a certain number on a spinner depends on two things. Firstly, it depends on how many times each number appears. For example, on this spinner, we can see that the number nine appears twice. So we might think that it’s more likely that we might get the number nine.

The other important thing to think about is the size of each section. The larger the section, the more likely we are to land on it. And so this phrase is a very important part of the question. Each section on the spinner is equally likely to be chosen. What this phrase is telling us is that each section is exactly the same size. So we have a circle. And it’s split into five equal parts. Each part is a fifth of the whole.

So what’s the probability that if we spin the arrow, it will land on the number four? Because all the sections are the same size, we can see that the chance of the arrow stopping in this position is one out of a possible five. And how can we write this as a fraction? One out of a possible five is one-fifth which is already written in its simplest form. So the chance of us spinning a four is one-fifth.