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Math Help - Percents

  1. #1
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    Percents

    A number is increased by 25% and the resulting number is then decreased by 20%. The final number is what percent of the original number?

    I know the answer is 100 but how do I show it?
    Last edited by mr fantastic; March 23rd 2010 at 03:22 AM. Reason: Restored deleted question.
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  2. #2
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    Quote Originally Posted by donnagirl View Post
    A number is increased by 25% and the resulting number is then decreased by 20%. The final number is what percent of the original number?

    I know the answer is 100 but how do I show it?
    Dear donnagirl,

    Suppose your number is x, then when it is increased by 25% the resulting number is,

    x+\frac{25x}{100}

    Then the result is decreased by 20% that is,

    \left(x+\frac{25x}{100}\right)-\frac{20}{100}\left(x+\frac{25x}{100}\right)=\frac  {5x}{4}-\frac{1}{5}\left(\frac{5x}{4}\right)=x

    So the number is 100% of the original number.

    Hope this will help you.
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