need algebraic formula help

Discussion in 'Green Room' started by Perris Calderon, Nov 6, 2009.

  1. Perris Calderon

    Perris Calderon Moderator Staff Member Political User

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    here's the problem, which I can obviously solve through trial and error but I want to see if there's a formula that solves the problem

    a+b=19859 where b = a x .08625

    here's where the formula comes from;

    the buy out on my car is 19859 which includes tax, I would like to know the number before tax, tax is 8.625%

    so I don't need the formual I need to know the process for arriving at the solution

    '[edit]

    got it, tax is not .08625 it's 1.08625

    problem solved, I just devide the final number by tax as 1.08625 and I'm good
     
  2. fitz

    fitz Just Floating Along Staff Member Political User Folding Team

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    actually, tax is still .08625 -while the way you solved it is the proper way to solve it, it always helps to see the reason you do that.. you're not really dividing it by tax as 1.08625, your solving for "a"

    The solution actually goes:

    Code:
    19859 = a + b
    
    but since b = a * .08625 (or, b = .08625a) then:
    
    19859 = a + 08625a
    19859 = a(1 + .08625)
    19859 = a(1.08625)
    
    so 19859/1.08625 = a
    
    
     
  3. Perris Calderon

    Perris Calderon Moderator Staff Member Political User

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    nice, thanx for the explanation!

    but where did you get "1" from?
     
    Last edited: Nov 9, 2009