SOLUTION: To get an A in her math course, Tina needs, the average of five tests to be at least 90. Her current test scores are 80, 91, 85, and 84. What range of scores on the fifth test woul

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Question 993161: To get an A in her math course, Tina needs, the average of five tests to be at least 90. Her current test scores are 80, 91, 85, and 84. What range of scores on the fifth test would get her an A in the course? Please explain how I need to solve this and set the problem up
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
.
x=grade on fifth test.
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Average=%28sum_of_grades%2Fnumber_of_grades%29
.
So for average of 90 over 5 tests:
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90=%2880%2B91%2B85%2B84%2Bx%29%2F5
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90=%28340%2Bx%29%2F5
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90=%28340%2F5%29%2B%28x%2F5%29
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90=68%2Bx%2F5
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22=x%2F5
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110=x
.
ANSWER: She must score at least 110
on the fifth test to average 90 over the 5 tests.