Video: Determining the Probability of Compound Events Involving Spinners

If these two spinners are spun, what is the probability that the sum of the numbers the arrows land on is a multiple of 5?

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Video Transcript

If these two spinners are spun, what is the probability that the sum of the numbers the arrows land on is a multiple of five?

To find this probability, we’ll need to consider spinning the first spinner event one and spinning the second spinner event two, making this a compound event. If we want to know the probability that the sum of the spinners is a multiple of five, we need the multiple of five outcomes over the total outcomes. There are a few methods we could use. We could create a tree diagram for spinner one and spinner two. However, because we need to sum the results of spinner one and spinner two, a table is probably a better choice.

In the first row and the first column, we would add if spinner one landed on one and spinner two landed on two, this sum would be three. And then, we’ll consider as spinner one landed on one and spinner two landed on four. This sum would be five. We fill in the rest of our table with the correct sums. In the table, we have all possible outcomes. And we can circle the ones that are multiples of five.

We’ve identified five of the results that are multiples of five out of the 21 possibilities. The probability that the sum of the spinners is a multiple of five is five over 21. The fraction can’t be reduced any further, so five over 21 is the final answer.

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