SOLUTION: On the three tests of 100 points each, Takia has an 87 average. What is the lowest score she could earn on the next test to have an 90 average?

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Question 507026: On the three tests of 100 points each, Takia has an 87 average. What is the lowest score she could earn on the next test to have an 90 average?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let the scores of the first three tests be a, b, and c. Then:
%28a%2Bb%2Bc%29%2F3+=+87 To find the sum of the first three test scores, multiply both sides by 3.
a%2Bb%2Bc+=+261 Now let the fourth test score be x, so...
%28a%2Bb%2Bc%2Bx%29%2F4+%3E=+90 Substitute a%2Bb%2Bc+=+261
%28261%2Bx%29%2F4+%3E=+90 Multiply both sides by 4.
261%2Bx+%3E=+360 Subtract 261.
x+%3E=+99
Takia must score at least 99 points on the fourth test to achieve an overall average of 90.