SOLUTION: In a science test a class of 30 students had an average of 80. The 20 girls had an average of 85. Whats the average of the 10 remaining boys?

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Question 328054: In a science test a class of 30 students had an average of 80. The 20 girls had an average of 85. Whats the average of the 10 remaining boys?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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In a science test a class of 30 students had an average of 80.
The 20 girls had an average of 85.
What's the average of the 10 remaining boys?
:
Let x = av of the 10 boys
:
%2820%2885%29%2B10x%29%2F30 = 80
multiply both sides by 30, results
20(85) + 10x = 30(80)
1700 + 10x = 2400
10x = 2400 - 1700
10x = 700
x = 700%2F10
x = 70 is the av of the 10 boys