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### Sales and Taxes

```
Date: 03/11/2001 at 19:39:30
From: Aiziah
Subject: Sales and Taxes

I bought \$27.97 worth of food. The food tax is 5.5%. I'm trying to
find the tax I have to pay, and the total amount that I pay.
```

```
Date: 03/13/2001 at 01:09:50
From: Doctor Ian
Subject: Re: Sales and Taxes

Hi Aiziah,

There are a couple of ways that you might go about that. The usual way
would be to multiply the amount of the purchase (\$27.97) by the tax
(5.5%, or 0.055), and add the two together:

total = \$27.97 + 0.055 * \$27.97

= \$27.97 * (1 + 0.055)

= \$27.97 * 1.055

Another way to look at it is this: If the amount of the purchase were
exactly \$100, then you would have to pay exactly \$5.50 in tax. So the
amount of tax that you're actually going to pay is the same fraction
of \$5.50 that \$27.97 is of \$100:

tax    \$27.97
----- = ------
\$5.50    \$100

27.97 * 5.50
tax = -------------
100

5.50
= 27.97 * ----
100

= 27.97 * 0.055

which is the same thing we got with the first method. (That should
come as no surprise, right?)  Actually, this tells you _why_ the first
method works, which is a handy thing to know in case you forget some
of the tricks for working with percentages.

more, or if you have any other questions.

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Fractions
Elementary Word Problems
Middle School Fractions
Middle School Word Problems

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