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Math Help - percentages and reversing them

  1. #1
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    percentages and reversing them

    hi,
    how can i do this...

    i did this...

    10x0.8=8

    then to reverse it i tied this

    8x1.2=9.6

    so how can i undo both of these to get back to 10?

    thanks
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  2. #2
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    Quote Originally Posted by benhathaway View Post
    hi,
    how can i do this...

    i did this...

    10x0.8=8

    then to reverse it i tied this

    8x1.2=9.6

    so how can i undo both of these to get back to 10?

    thanks
    Hello,

    the reciprocal value of 0.8 is 1.25:

    \frac{1}{0.8} =  1.25

    and

    8 \cdot 1.25 = 10
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  3. #3
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    this is for a shopping cart and i reduced all my items by 20% using the price x 0.8. Then i tried to make it back up by doing this price x 1.2. But this didnt work so how can get the original price back?
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  4. #4
    GAMMA Mathematics
    colby2152's Avatar
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    Quote Originally Posted by benhathaway View Post
    this is for a shopping cart and i reduced all my items by 20% using the price x 0.8. Then i tried to make it back up by doing this price x 1.2. But this didnt work so how can get the original price back?
    As earboth showed, you must multiply it by 1.25 (1 / 0.8)
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  5. #5
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    hi,
    the only problem is that i have the price that has allready been discounted by 20% and multiplied by 1.2. This cannot be reversed! Now i have tried to multiply by 1.25 so i need to reverse this...

    price x 0.8 x 1.2 x 1.25

    Thanks
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  6. #6
    GAMMA Mathematics
    colby2152's Avatar
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    Quote Originally Posted by benhathaway View Post
    hi,
    the only problem is that i have the price that has allready been discounted by 20% and multiplied by 1.2. This cannot be reversed! Now i have tried to multiply by 1.25 so i need to reverse this...

    price x 0.8 x 1.2 x 1.25

    Thanks
    You want the price back to normal?

    .8*1.2*1.25*y = 1
    1.2y=1
    y=.8333 OR 5/6
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