Question

If a student has an average exam score between 70 and​ 79, he will earn a grade of C in his algebra course. Suppose he has three exam scores of 75 ​, ​62, and 85 and that his teacher said the final exam score has twice the weight of the other three exams. What range of scores on the final exam will result in him earning a grade of​ C?

Answer 1

(64,86.5)

Explanation:

find the case where he gets 70 and the case where he gets 79

if his average is 70:

(75+62+85+2x)/5=70

(222+2x)/5=70

222+2x=350

2x=128

x=64

if his average is 79:

(75+62+85+2x)/5=79

(222+2x)/5=79

222+2x=395

222+2x=395

2x=173

x=86.5