Practice Problem 2: Girl or Senior? A local high school has 1400 students; 800 of whom are girls. 300 of the students are seniors; of which 200 are girls. If we chose a student at random, what is the probablety that we would choose a girl or a senior? Step 1: List the events. Event A: Event B: Step 2: Decide if the events are mutually exclusive or not. The events mutually exclusive because one student be a girl and a senior at the same time. Step 3: Write the correct equation and solve for the probability. The events are not mutually exclusive, so we should use the equation because P(A and B) # 0. How many total students attend the school? students P(G or S) = P(G) + P(S) - P(G and S) P(G or S)= 200 1400 1400 P(G or S) = P(G or S) = 1 The probability of choosing a student who is a girl or a senior is -. This means that 9 out of ever students is a girl, a senior, or both