SOLUTION: An average grade of 80 on all exams in a course is needed to earn a B in the course. On her first four exams, Chuck’s grades are 96, 65, 79, and 87. What is the minimum grade that

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Question 1119691: An average grade of 80 on all exams in a course is needed to earn a B in the course. On her first four exams, Chuck’s grades are 96, 65, 79, and 87. What is the minimum grade that Chuck can receive on the fifth exam to earn a B in the course?
Found 3 solutions by josgarithmetic, ikleyn, greenestamps:
Answer by josgarithmetic(39618)   (Show Source): You can put this solution on YOUR website!

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Answer by ikleyn(52794)   (Show Source): You can put this solution on YOUR website!
.
 = 80


96 + 65 + 79 + 87 + x = 80*5


x = 80*5 - (96 + 65 + 79 + 87) = 73.


Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!


When solving a question like this, involving averages of numbers that are all close together, a method that can get you to the answer faster is to compare the given numbers to the desired average.

In this case, with a desired overall average of 80, the current scores are
96  = +16
65  = -15
79  = - 1
87  = + 7
     ----
      + 7

Overall, the current scores have a "balance" of +7 compared to the desired average.

To obtain the desired average (or better), the minimum score on the 5th test must have a "balance" of -7.

So 80-7 = 73 is the minimum score needed on the 5th test to get an overall average of 80 or higher.
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