Solve the problem.
-Michael scored 68, 88, and 91 on three algebra tests. What must he score on the fourth test in order to have an average grade of at least 85?
A)62
B)29
C)93
D)82

Question

Quizplus · Accepted Answer

To have an average grade of at least 85, Michael's total score on all four tests must be at least (85 x 4) = 340.

His current total score on the first three tests is (68 + 88 + 91) = 247.

Therefore, he must score at least (340 - 247) = 93 on the fourth test to have an average grade of at least 85. Let x be the score on the fourth test. Michael's average on four tests will be (68+88+91+x)/4. Since this average must be at least 85, we can write the inequality: 
(68+88+91+x)/4 ≥ 85 
Simplifying and solving for x: 
(247+x)/4 ≥ 85 
247+x ≥ 340 
x ≥ 93 
Therefore, Michael must score at least 93 on the fourth test to have an average grade of at least 85. Choice C is the correct answer.

Solve the Problem. -Michael Scored 68, 88, and 91 on Three Algebra Tests