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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):
Answer by ikleyn(52794)  (Show Source):
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
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+ 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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