In this lesson, students apply the addition rule to relate the probabilities of combined events. Students develop the addition rule by using tables of outcomes and by comparing the sum of the outcomes in individual events to the number of outcomes in the combination. The addition rule states that given events A and B, .

When students use the addition rule to get an answer and then interpret the meaning of their answer in a context, then they are reasoning abstractly and quantitatively (MP2). When students have to fix or find the error and explain the correct reasoning, they are constructing viable arguments and critiquing the reasoning of others (MP3).

Technology isn't required for this lesson, but there are opportunities for students to choose to use appropriate technology to solve problems. We recommend making technology available.