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Math Help - Averages (Mean)

  1. #1
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    Averages (Mean)

    I am trying to find the average of these test scores:


    83

    85

    86

    100 (this one is worth 25%, however)


    I don't know how to do this because of the special one
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  2. #2
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    Re: Averages (Mean)

    What "special one"? You do know that 100/4= 25, don't you? If one is worth 25% then the other three must total 75%. And each one must be worth what?
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  3. #3
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    Re: Averages (Mean)

    Sorry, I meant that the the first three are worth a normal grade.

    The last one is worth 25% of one of the first three.
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  4. #4
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    Re: Averages (Mean)

    I think I got it. Can someone verify?

    (.3125*83) + (.3125*85) + (.3125*86) + (.0625*100) = 85.6%
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  5. #5
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    Re: Averages (Mean)

    No. If the last is worth 0.0625 and the others are worth four times as much, the others would be worth 4(0.0625)= 0.25, not 0.3125. And .25+ .25+ .25+ .0625 does not add up to 100%. I think you mistakenly took 1/4 of 1/4 to get 1/16 and the divided the remaining 15/16 by 3 to get 5/16 for each of the original three. You mistake was treating the first three as 1/4 each when you knew from the start that you were NOT dividing these equally.

    Call the value of each of the first three "a" the last is worth "a/4". So we must have a+ a+ a+ a/4= 3a+ a/4= (12a+ a)/4= 13a/4= 1.00 so a= 4/13. each of the first tests is worth 4/13 and the last text is worth 1/4 of that, 1/13.
    Thanks from Gragadoodle
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  6. #6
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    Re: Averages (Mean)

    (0.30769230769*83)+(0.30769230769*85)+(0.307692307  69*86)+(0.07692307692*100) = 85.8%


    There we go! Thanks!
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