finding average in an inequality word problem

Question

Sam wants to earn at least a B in Math. If he earned the following percents 100, 82 ,70 , 72, 80. What is the minimun grade Sam must earn in order to keep a B average? (Hint: grade b is an 80 an greater  an less than a 90 )

 A: write an solve an algebraic inequality . Show all your work

B:answer the question in the problem an label.

Answer 1

Let the grade required be x.

80 < (100 + 82 + 70 + 72 + 80 + x) / 6 < 90

Solving, we have:

80 < (404 + x) / 6 < 90
480 < 404 + x < 540
480 - 404 < x < 540 - 404
76 < x < 136
76 < x <= 100 [Note that 100 is the maximum marks you can get]