SOLUTION: you have the following grades on your biology test 88, 85, 91 and 92. you have one more test to take and you want to get a final average of 90 on your test. what do you need to get

Question 514009: you have the following grades on your biology test 88, 85, 91 and 92. you have one more test to take and you want to get a final average of 90 on your test. what do you need to get on your final test in order to have an average of 90?
Answer by drcole(72) (Show Source): You can put this solution on YOUR website!
Let x be the grade on the last test. The average of the five test grades is therefore:

We want this average to be 90, so we set it equal to 90 and solve for x:

(combine like terms)
(multiply both sides by 5)
(subtract 356 from both sides)
So you need a 94 on the last exam to get a 90 average on all five exams. Make sure to check that the average of the five exams is indeed 90!
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