Solve. Use interval notation to express the range.
-On the first four exams, your grades are 79, 89, 68, and 80. You are hoping to earn a C in the course. This will occur if the average of your five exam grades is greater than or equal to 70 and less than 80. What range of grades on the fifth exam will result in earning a C?
A) (24, 74]
B) [34, 84)
C) (34, 84]
D) [24, 74)

Question

Quizplus · Accepted Answer

To find the range of grades for the fifth exam that results in a C, we first calculate the total points needed for an average between 70 and 80 over five exams. The total points for the first four exams are 79 + 89 + 68 + 80 = 316. For an average of 70, the total points needed are 70 * 5 = 350, so the fifth exam needs to be at least 350 - 316 = 34 points. For an average just below 80, the total points needed are 80 * 5 = 400, so the fifth exam can be up to 400 - 316 = 84 points, but not including 84 since the average must be less than 80. Therefore, the range of grades on the fifth exam that results in earning a C is [34, 84).

Solve. Use Interval Notation to Express the Range