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Question 6902: A student has earned scores of 87, 81, and 88 on the first 3 of 4 tests. If the student wants an average (arithmetic mean) of exactly 87, what score must she earn on the fourth test?
Answer by bonster(299)   (Show Source):
You can put this solution on YOUR website! If we have four tests who's mean is 87, we know that we can multiply 87x4 to find out what the student's total score is.
87x4=348.
Now, we know that the first three scores are 87, 81, and 88. We don't know what the fourth score is so we'll use "x".
Add the four and that would equal 348 (348 is from multiplying 87 & 4):
87 + 81 + 88 + x= 348
256+x=348 (subtract 256 from both sides)
x=92
The fourth test score must be 92.
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