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Math Help - Percentages

  1. #1
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    Percentages

    Hi al. I have a problema. I know it is possible with a very simple operation. This is the problema: I have a value, I want to add a percentage to it, and then remove that percentage but now of the new value and keep the original value: if I have 100, add 15%, it gives me 115, but now if I take the 15% of the 115, I have 97.75. I want the formula to add the initial 15% in such way that I can take 15% of the total value and keep the original 100. Any help please? Regards Virginio Reis P.S. Some how the fórum does not accept the carriage return, so the post goes in a single line.
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  2. #2
    Junior Member Bradyns's Avatar
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    Maitland, NSW, Australia
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    Re: Percentages

    Let's call the starting value 'x'
    Let's call the final value 'y'

    x * 1.15 will give you the 115% (your 115 value)

    (x * 1.15)*(0.85) will give you 15% off the value of 115% (your 97.75 value)

    So, you can write the expression as:
    1.003x = y

    What you seem to be asking for is bizarre, as you would simply be multiplying by 1.

    \frac{x\times 1.15}{1.15}=x
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  3. #3
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    Re: Percentages

    Is not bizarre. Supose you have a business and a guy help you on selling something, but you have to give him/her a 10% comission. You want to keep the original value for yorself and past the comition for the customer. I foud the solution meanwile: 100/0.9 = 111.11. Now 10% of 111.11 is 11.11. 111.11 - 11.11 = 100. There it goes. You give the vendor the comission and you keep your money.
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