SOLUTION: The average age of 80 boys in a class is 15. The average age of a group of 15 boys in the class is 16 and the average age of another 25 boys in the class is 14. What is the average

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Question 792173: The average age of 80 boys in a class is 15. The average age of a group of 15 boys in the class is 16 and the average age of another 25 boys in the class is 14. What is the average age of the remaining boys in the class?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The average age of 80 boys in a class is 15.
The average age of a group of 15 boys in the class is 16
and the average age of another 25 boys in the class is 14.
What is the average age of the remaining boys in the class?
:
Find the number of remaining boys: 80 - 15 - 25 = 40
:
Let x = the average age of the remaining 40 boys
:
%28%28%2840x%29+%2B+15%2816%29+%2B+25%2814%29%29%29%2F80 = 15
multiply both sides by 80
40x + 15(16) + 25(14) = 80(15)
40x + 240 + 350 = 1200
40x + 590 = 1200
40x = 1200 - 590
40x = 610
x = 610/40
x = 15.25 yrs average age of the 40 remaining boys