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Math Help - Percentages problem need help adding percentages please

  1. #1
    dix
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    Percentages problem need help adding percentages please

    I need 40% overall to pass my exam. So far I have got:

    55% of an exam worth 45% of overall grade, and
    75% of an essay worth 10% of overall grade

    I have one more exam, worth 45% of the overall grade. What is the minimum percentage score I need to achieve to get an overall grade of 40%?

    I have no idea how to do the math, so any help is great.

    Thanks
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  2. #2
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    Re: Percentages problem need help adding percentages please

    Quote Originally Posted by dix View Post
    I need 40% overall to pass my exam. So far I have got:

    55% of an exam worth 45% of overall grade, and
    75% of an essay worth 10% of overall grade

    I have one more exam, worth 45% of the overall grade. What is the minimum percentage score I need to achieve to get an overall grade of 40%?

    I have no idea how to do the math, so any help is great.

    Thanks
    Re-write the first percentages as decimal numbers. You'll get:

    0.55 \cdot 45\% + 0.75 \cdot 10\% + x \cdot 45\% =  40\%

    Solve for x and transform into a percentage.
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  3. #3
    dix
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    Re: Percentages problem need help adding percentages please

    Thanks earboth,

    I got:

    step 1) (0.55 x 45%) + (0.75 x 10%) + (y x 45%) = 40%
    step 2) 0.2475 + 0.075 + (y x 45%) = 40%
    step 3) 0.3225 + (y x 45%) = 40%
    step 4) 0.40 - 0.3225 = y x 45%
    step 5) 0.0775 = y x 45%
    step 6) 0.0775 / 0.45 = y
    step 7) y = 17.22%

    Is that correct? I'd only need around 17%?
    Last edited by dix; May 11th 2012 at 07:47 AM.
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  4. #4
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    Re: Percentages problem need help adding percentages please

    Yes, that is correct.
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