Price before Discount

Date: 6/3/96 at 18:16:4
From: George Dickenson
Subject: The price of a calculator

A calculator is discounted 20 percent. After adding 7 percent tax, the 
total cost is $20.07.  What was the list price of the calculator, 
without tax, before discount?

Date: 6/14/96 at 0:56:23
From: Doctor Brian
Subject: Re: math problems

When 20 percent is discounted from a price, you still have to pay 
80 percent of the original price.  When 7 percent tax is added to a 
price, you have to pay that plus 100 percent of what you normally 
would, for a total of 107 percent of the actual price.

We'll use these two ideas in the problem.

If x is the original price, then we are paying 107 percent of (the 
sale price), which is 107 percent of (80 percent of the original 
price).  And since the word "of" means "times" in percent problems, 
we get

   1.07 * .80 * x = 20.07

         .856 * x = 20.07

                x = 23.45

-Doctor Brian,  The Math Forum
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