Solve the problem.
-On the first four exams, your grades are 78, 90, 65, and 79. There is still a final exam, and it counts as two grades. You are hoping to earn a C in the course. This will occur if the average of your six exam grades is greater than or Equal to 70 and less than 80. What range of grades on the final exam will result in earning a C?
A)[38, 88]
B)[38, 88)
C)[54, 84)
D)[54, 84]

Question

Quizplus · Accepted Answer

To find the range of grades on the final exam that will result in earning a C, we calculate the average of all six grades. Let x be the grade on the final exam. The average is (78 + 90 + 65 + 79 + x + x) / 6. Simplifying, we get (312 + 2x) / 6. For a C, this average must be between 70 and 80. Solving 70 ≤ (312 + 2x) / 6 < 80 gives the range 54 ≤ x < 84.

Solve the Problem. -On the First Four Exams, Your Grades Are 78, 90