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Calculating Sales Tax

Date: 09/19/2001 at 12:03:35
From: Jason 
Subject: Sales Tax

How do I calculate sales tax? Please describe the steps.

Date: 09/19/2001 at 15:30:08
From: Doctor Ian
Subject: Re: Sales Tax

Hi Jason,

First, you have to know the tax rate -- for example, 5 1/4 percent.

The idea is that for each 100 units that you spend, you have to pay 
5 1/4 units in tax. So the ratio

  tax     5 1/4
  ----- = -----
  price    100

You can multiply both sides of the equation by price to get

        5 1/4
  tax = ------ * price

which is how you compute the tax. Note that this is the same as 
dividing the price into 100 parts, and paying an amount equal to 5 1/4 
of those parts in tax:

  tax = (price / 100) * 5 1/4

Does this help? 

- Doctor Ian, The Math Forum   
Associated Topics:
Middle School Fractions
Middle School Ratio and Proportion

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