A teacher gave the same test to three history classes: A, B, and C.
A teacher gave the same test to three history classes: A, B, and C. The average (arithmetic mean) scores for the three classes were 65, 70, and 77, respectively. The ratio of the numbers of students in each class who took the test was 4 to 6 to 5, respectively. What was the average score for the three classes combined?
Answer/Solution
71
Steps/Work
ratio is 4:6:5 , numbers are 4x, 6x, 5x
total scores of each class is (65*4x + 6x * 70 + 77*5x) = 260x+420x+385x = 1065x
total number of students = 15x
average = 1065x/15x = 71
A is the answer
total scores of each class is (65*4x + 6x * 70 + 77*5x) = 260x+420x+385x = 1065x
total number of students = 15x
average = 1065x/15x = 71
A is the answer