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Math Help - Help with (mean) problem.

  1. #1
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    Help with (mean) problem.

    I would like to know the process of finding the answer to this problem.

    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? Thankyou.
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by birdie41 View Post
    I would like to know the process of finding the answer to this problem.

    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? Thankyou.
    Assume the 4th score is x. Then the average of the four scores would be:
    \frac{87+81+88+x}{4} = 87

    256 + x = 348

    So x = 92.

    -Dan
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    How did you get 348?
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by birdie41 View Post
    How did you get 348?
    Sorry, I should have written that step out. Here's the whole thing:
    \frac{87+81+88+x}{4} = 87

    \frac{256+x}{4} = 87

    4 \cdot \frac{256+x}{4} = 4 \cdot 87

    256 + x = 348

    256 + x - 256 = 348 - 256

    x = 92

    -Dan
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