SOLUTION: A student scores 86, 98, 91, 94, and 83 on five exams where 100 is perfect. The final exam counts as much as two regular exams. What score does the student have to make on the fina

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Question 224479: A student scores 86, 98, 91, 94, and 83 on five exams where 100 is perfect. The final exam counts as much as two regular exams. What score does the student have to make on the final to have a 90% average for the course?
Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = score on final exam.

Add the scores together, including 2x for the final exam since it counts twice, and divide by 7 grades. The average is supposed to be 90.

%2886%2B98%2B91%2B94%2B83%2B2x+%29%2F7=90

Multiply both sides by 7:
%2886%2B98%2B91%2B94%2B83%2B2x%29=630
452%2B2x=630
2x=178
x=89

R^2

Dr. Robert J. Rapalje