SOLUTION: Two high school classes took the same test. One class of 20 students made an average grade of 80%; the other class had an average grade of 70%. If the average grade for the combine

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Question 772918: Two high school classes took the same test. One class of 20 students made an average grade of 80%; the other class had an average grade of 70%. If the average grade for the combined classes was 74%, how many people were in the second class?
Answer by lwsshak3(11628) About Me  (Show Source):
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Two high school classes took the same test. One class of 20 students made an average grade of 80%; the other class had an average grade of 70%. If the average grade for the combined classes was 74%, how many people were in the second class?
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let x=number of students in the 2nd class
In the first class 20 students had a cumulative score=20*80=1600
In the 2nd class x number of students had a cumulative score=x*70
combined classes had a combined cumulative score=1600+70x
20+x=total number of students in both classes
..
%2820%2A80%2B70x%29%2F%2820%2Bx%29=74
1600%2B70x=1480%2B74x
4x=120
x=30
how many people were in the second class? 30