# Need help understanding Sales Tax Rate

• Dec 26th 2010, 06:42 PM
Shortstop13
Need help understanding Sales Tax Rate
I'm extremely thick headed for some reason so help would be appreciated.

Ok so lets say I paid \$22.69 for a pizza. The sale tax rate is 8%. Now I need to find the price of the pizza alone.

My question is, why can't I just subtract 8% from the 22.69 to get my answer? When I read the problem, that's the first solution my brain comes up with (to just subtract 8% off the price that already has 8% added to it.)
• Dec 26th 2010, 06:45 PM
dwsmith
\$\displaystyle (price \ of \ pizza)*(1+tax)=22.69\$
• Dec 26th 2010, 06:56 PM
Shortstop13
Yeah I have the proper way to do the problem right in my book, I've done a dozen problems like this.

It's just that now I'm at a word problem section and I don't understand WHY I have to do it that way. When I read it as a word problem, my first instinct is to find 8% of the \$22.69 and subtract it off the \$22.69. I know it sounds crazy, I just can't figure out WHY I have to do that way and it's really getting under my skin lol.
• Dec 26th 2010, 06:59 PM
dwsmith
8% of the total is 8% of the pizza and 8% of the tax.

The pizza cost x dollars.

We know x dollars + 8% of x dollars = the total.

Tax = x*.08

x+x*.08=x(1+.08)=total

I just factored out the x.
• Dec 26th 2010, 07:00 PM
Shortstop13
Alright thanks, I'll read that a few times.