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

Algebra ->  Average -> 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      Log On


   

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) About Me  (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:
+%2888+%2B+85+%2B+91+%2B+92+%2B+x%29%2F5+
We want this average to be 90, so we set it equal to 90 and solve for x:
+%2888+%2B+85+%2B+91+%2B+92+%2B+x%29%2F5+=+90+
+%28356+%2B+x%29%2F5+=+90+ (combine like terms)
+356+%2B+x+=+450+ (multiply both sides by 5)
+x+=+94+ (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!