SOLUTION: An average score of 80 to 90 in a math class receives a B grade. A student has scores of 92, 66, 72 and 88 of four tests. Find the range of scores on the fifth test that will give

Question 662795: An average score of 80 to 90 in a math class receives a B grade. A student has scores of 92, 66, 72 and 88 of four tests. Find the range of scores on the fifth test that will give the student a B for the course.

Found 2 solutions by lynnlo, KMST:
Answer by lynnlo(4176) (Show Source): You can put this solution on YOUR website!
92,66,72,88,90=408 divided by 5 test =81.6
you will need 90
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
I interpret the wording as meaning that 80 and 90 are both a B.
I'll solve based on that.

WITH ROUNDING:
If we are going to be realistic, we have to consider rounding.
I expect that an average of 79.5 would be rounded up to 80, and would be enough for a B.
I expect that an average of 90.5 would be rounded up to 91, and that would be enough for an A,
but any average of less than 90.5 (even a 90.4) would be a B.
So I am starting from

I am assuming they calculate the average as the sum of all tests grades divided by the number of tests.
If the score in the last test is , the average will be

Now my equation is

Multiplying all sides of the signs times 5, we get an equivalent inequality
-->
Subtracting from all sides of the signs, we an the equivalent inequality
--> -->
So there is no possibility of getting an A, and a score of in the fifth test is needed to get an A as the final grade.

WITH ROUNDING:
If the average has to be exactly 80.0 for a B,
then --> --> , and an in the fifth test is needed for a B.
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