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Help with an algebra equation

  1. Jun 28, 2008 #1
    I'm 58 and I'm afraid my math skills are not what they used to be. I have been working on this problem for days now and have the correct answer, but only by trial and error. I'm working on a spreadsheet that will calculate a discount off a base price. All I have is the total price, which includes a service cost of .006 of the base price + a 15% tax on the service cost. In order to do this I need to know the base price. Since the total price includes the 15% tax, I need to be able to calculate the tax amount, deduct it and then calculate the service cost. How do I calculate the tax before I know the base price or the service cost? This is the best as I can represent it in a formula:

    x = 998,500 - (.15y)
    y = x/1.006

    Any assistance would be appreciated.
  2. jcsd
  3. Jun 28, 2008 #2
    Hello, as far as I cant understand your question:

    you have the total cost, let us call this Tc, this Tc is made up from a base price, let us call this B, and also a Service cost, let us call this S, and a Tax on the service cost let us call this Tx, thus:

    T_{c} = B+S+T_{x}

    and [tex]T_{x} = 0.15B[/tex]

    and [tex]S = B-0.006[/tex] thus:

    [tex]T_{c} = B + (B-0.006) + (0.15B)[/tex]

    and I assume you wish to calculate the base price?
    Last edited: Jun 28, 2008
  4. Jun 28, 2008 #3
    Thank you for your assistance. The way you diagrammed it is correct, with the exception that Tx = .15S. I need to know B, that way I can calculate S and Tx easily.
  5. Jun 28, 2008 #4


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    Welcome to PF!

    Hi Iguanahump! Welcome to PF! :smile:

    If I've understood it right:

    S = 0.006B;

    tax = 0.15S = 0.15 0.006B = 0.0009B;

    so total = B + S + tax = B(1 + 0.15 + 0.0009) = 1.1509B. :smile:
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