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# Last I Promise

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Andy and Suzy go to Westwood Middle School 7th Grade. Danny and Joseph go to Baldwin Middle School 7th Grade. The age range of the students in 7th Grade at Westwood is 12-13 years of age, with 12 years old being 40% of the class, and 13 years old being 60% of the class. The age range of the students in 7th Grade at Baldwin is also 12-13 years of age, with 12 years old being 70% of the class, and 13 years old being 30% of the class. What is the probability that all four of these students are of the same age?

Nov 13, 2018

$$P[\text{all same age}] = P[\text{all 12}] + P[\text{all 13}] = \\ (0.4)^2(0.7)^2 + (0.6)^2(0.3)^2 = 0.1108$$