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Answer:
C. 98
Step-by-step explanation:
If you add all of his previous test scores and go through the list of numbers you get C.98 as the answer. I added all of his test scores plus 98 which equals 630 divided by 7 (because if he got a 98 there would be 7 test scores) you would get 90 or an A average.
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Explanation:
Let x be the next test grade. It ranges from 0 to 100, inclusive of both endpoints.
The original set {87,92,90,84,88,91} becomes {87,92,90,84,88,91,x} after adding on that score.
We have 7 scores now. We find the average by adding up those seven scores and dividing by 7.
average = (sum of the scores)/(number of scores)
average = (87+92+90+84+88+91+x)/7
average = (532+x)/7
We want the average to be 90 or higher, so we would then have these steps
[tex]\text{average} \ge 90\\\\\frac{532+x}{7} \ge 90\\\\532+x \ge 90*7\\\\532+x \ge 630\\\\x \ge 630-532\\\\x \ge 98\\\\[/tex]
This means Edgar must score a 98 or higher on the seventh test in order for his overall average to be 90 or higher.
In other words, the lowest test score he can get is a 98.
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Extra info (optional section):
Let's say Edgar gets the highest score possible.
So he gets x = 100
This would mean
average = (87+92+90+84+88+91+x)/7
average = (532+x)/7
average = (532+100)/7
average = 632/7
average = 90.2857 which is approximate
We can see that his overall average would stick to 90 if the teacher is rounding to the nearest whole number.