Sales and TaxesDate: 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. I hope this helps. Write back if you'd like to talk about this some more, or if you have any other questions. - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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