math problem not for school?

Y

Yan

New member
A total of 50 juniors and seniors were given a mathematics test. The 35 juniors attained an average score of 80 while the 15 seniors attained an average of 70. What was the average score for all 50 students who took the test?

Please sovle and show work i think its 75 but the answer key in the book tells me its 77. How do i get the answer?
 
(35 Juniors x 80 Average) = 2800
(15 Seniors x 70 Average) = 1050

2800 + 1050 = 3850

3850 divided by 50 (total number of students) = 77.

You have to do it like this because this accounts for the average of each individual in the group of fifty, not the average between the two grades (which is 75).
 
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