SOLUTION: To get a C you need an average between 70-80. Kims scores are 76, 60, and 87 on each 100 point test. What scores are possible for the fourth test so she will have a C.

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Question 190518: To get a C you need an average between 70-80. Kims scores are 76, 60, and 87 on each 100 point test. What scores are possible for the fourth test so she will have a C.
Answer by jonvaliente(64) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=Kim's possible test score
.
Average=SUM of test scores/no of tests
.
Kims total test scores for 3 exams=76+60+87=223
.
To get a C, we need an average>=70 and <=80
.
70%3C=%28223%2Bx%29%2F4%3C=80
.
Multiplying all the terms by 4, we get:
.
70%2A4%3C=%28%28223%2Bx%29%2A4%29%2F4%3C=80%2A4
280%3C=223%2Bx%3C=320
.
Subtracting 223 from all terms we get:
.
280-223%3C=223-223%2Bx%3C=320-223
57%3C=x%3C=97
.
Therefore, Kim must get a score between 57 and 97 on her fourth test to get a C