Question

a student must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of B. Devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a B in the course? ( assuming the highest grade is 100%)

Answer 1

89–100

Explanation:

Let x represent the grade on the fifth test. The average for 5 tests wants to be between 80 and 90, so we have ...

80 ≤ (78 +62 +91 +80 +x)/5 ≤ 90

Multiplying by 5 gives

400 ≤ 311 +x ≤ 450

Subtracting 311 gives the range for the fifth test grade.

89 ≤ x ≤ 139

Since the maximum available score is 100, the range on the 5th test for an overall B grade is ...

89 ≤ x ≤ 100 . . . . where x is the grade on the 5th test