Question

A student must have an average​ (the mean) on five tests that is greater than or equal to​ 80% but less than​ 90% to receive a final grade of
b.​ devon's grades on the first four tests were​ 92%, 82%,​ 88%, and​ 92%. what range of grades on the fifth test would give him a b in the​ course?

Answer 1

46 <= grade < 96 First, let's write the equation for the lower limit that the student must get for a B. (x + 92 + 82 + 88 + 92)/5 = 80 Multiply both sides by 5 giving x + 92 + 82 + 88 + 92 = 400 Subtract 92, 82, 88, 92 from both sides x = 400 - 92 - 82 - 88 - 92 = 46 So the student has to get 46 or higher on the test to make a B. Now let's compute the upper limit (x + 92 + 82 + 88 + 92)/5 < 90 Multiply both sides by 5 (x + 92 + 82 + 88 + 92) < 450 Subtract 92, 82, 88, 92 from both sides x < 450 - 92 - 82 - 88 - 92 ) = 96 So the student has to get a grade of less than 96 to get a B.