2021 AMC 12B Problems/Problem 4
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Problem
Ms. Blackwell gives an exam to two classes. The mean of the scores of the students in the morning class is , and the afternoon class's mean score is . The ratio of the number of students in the morning class to the number of students in the afternoon class is . What is the mean of the scores of all the students?
Solution
WLOG assume there students in the morning class and in the afternoon class. Then the average is