SOLUTION: you want to calculate what you need on a 4th exam so you can receive at least a 70% in your math class. your previous three exam scores were 78%, 67%, 60%. your instructor calculat

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Question 692366: you want to calculate what you need on a 4th exam so you can receive at least a 70% in your math class. your previous three exam scores were 78%, 67%, 60%. your instructor calculates your grad by finding the mean of your four exams
Answer by KMST(5347) About Me  (Show Source):
You can put this solution on YOUR website!
x%=grade in the 4th exam
The calculated grade (in %) will be
%2878%2B67%2B60%2Bx%29%2F4=%28205%2Bx%29%2F4.
For a 70% grade,
%28205%2Bx%29%2F4=70 --> 4%2A%28205%2Bx%29%2F4=470 --> 205%2Bx=280 --> 205%2Bx-205=280-205 --> highlight%28x=75%29
You need at least a highlight%2875%29% in your 4th exam for a 70% grade.

You could also write it as inequalities:
For at least a 70% grade,
%28205%2Bx%29%2F4%3E=70 --> 4%2A%28205%2Bx%29%2F4%3E=470 --> 205%2Bx%3E=280 --> 205%2Bx-205%3E=280-205 --> highlight%28x%3E=75%29