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Math Help - Working backwards with percentages

  1. #1
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    Working backwards with percentages

    There is one type of question to do with percentages that I just can't get my head around. Below is an example:

    Staff at a computer game store get a discount of 21% on games. Bill bragged to his parents that he saved $102 last year. How much did Bill spend last year on games?

    I have been given the answer as $383.71 but for the life of me I can't work out how they got it.

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  2. #2
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    Quote Originally Posted by MikeChch View Post
    There is one type of question to do with percentages that I just can't get my head around. Below is an example:

    Staff at a computer game store get a discount of 21% on games. Bill bragged to his parents that he saved $102 last year. How much did Bill spend last year on games?

    I have been given the answer as $383.71 but for the life of me I can't work out how they got it.

    Hi Mike,

    The amount that he saved is 21% of total.

    The amount he spent was 79% of total.

    1% of total is

    \frac{102}{21}

    79% of total is

    \frac{102(79)}{21}
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