Real-Life Scenarios
Text Version

(Introduction music)
Image description:  Justyce, Marissa, Allyson, Andrew and Khalid are sitting in a baseball stadium watching a game. The scene opens with baseball players on the field and then transitions to the jumbotron screen advertising free tickets, a t-shirt and a hat. Allyson points to the jumbotron screen.

Allyson:  Wow, I would love to win a t-shirt or a hat.

Justyce: When is your birthday?

Allyson:  May.  What do you think my chances are of winning a t-shirt or a hat?

Justyce:  Let’s see.  It looks like there are 37 seating sections.  So the probability of you winning a t-shirt should be one-thirty-seventh or about two and seven-tenths percent.

Image description: Justyce takes out her calculator and types one divided by 37. The result shown on the calculator is the repeating decimal 0.027. Allyson takes the calculator and types in one divided by 12. The result shown on the calculator is 0.083 (with 3 repeating).

Allyson:  And since there are 12 months in the year, the chance of me winning a hat is one-twelfth or about 8 and three-tenths percent.

Justyce:  Okay, so to calculate the probability of winning a t-shirt or a hat we need to add these probabilities together, then subtract the probability of winning both.

Allyson:  Well, the probability of winning both would be the product of the two, so one-thirty-seventh times one-twelfth equals one-four hundred forty-fourth.

Image description: Allyson writes the equation one-thirty-seventh times one-twelfth equals one-four hundred forty-fourth.

Justyce: Now we need to use the Addition Rule.  So the probability of winning a t-shirt or a hat is the equation one-thirty-seventh plus one-twelfth minus one-four hundred forty-fourth equals four-thirty-sevenths.  So you have about a 10 and 8 tenths percent chance of winning a t-shirt or a hat.

Image description: Justyce writes the equation on paper as she describes it. She then completes the final calculation on her calculator, showing the repeating decimal 0.108.

Andrew:  That’s much better odds than any of us winning free tickets!