To get a final grade of B, a student must have an average mark on five tests that is greater than or equal to 80 and less than 9
0. If Lisa's grades on the first four tests were 97, 93, 78 and $7, solve for the range of grades x that she could score on the fifth test that would result in her getting a final grade of B.
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.
