SOLUTION: “student must have an average(the mean) on five tests that is greater than or equal to 80% but less than 90% to recieve a final grade of a B Devons grades on the first four tests

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Question 619350: “student must have an average(the mean) on five tests that is greater than or equal to 80% but less than 90% to recieve a final grade of a B Devons grades on the first four tests were 76%,65%,90%, and 80%What range of grades on the fifth test would give him a B in the course?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

first four tests(80% of grade) were 76%,65%,90%, and 80%   Average = 77.75

student must have an average(the mean) on five tests that is greater than 

or equal to 80% but less than 90% to recieve a final grade of a B

 .80(77.75) + .20x ≥ .80

               .20x ≥ 80 - 62.8

                  x ≥ 17.2/.2

                  x ≥ 86  ***** B the highest grade possible



              .20x < 90 - 62.8

                 x ≥ 27.2/.2

                  x ≥ 138%