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Myke
New Member

USA
2 Posts

Posted - 04/09/2011 :  10:54:14  Show Profile  Reply with Quote
trying to help my daughter with a math question
Linda is at a restaurant, she has $30 must pay 7% tax and wants to leave 15% tip, what is the most she can pay for a meal. I know the meal is $24.59 tip is $3.69 and tax is $1.72, I just don't know how to get there? What is the formula?
Thanks for any help.
Myke
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Ultraglide
Advanced Member

Canada
299 Posts

Posted - 04/09/2011 :  12:25:06  Show Profile  Reply with Quote
What you are trying to do is find the price before the tax and tip are added. In this question, you are assuming that the tax and tip are both based on the cost of the meal. (You are not basing your tip on the tax.) In this case, the tax and tip add up to 22%.


Here's an example: Say I bought an item for $1.50 and had to pay 6% tax. Now $1.50x6%=$0.09 which gives a final price of $1.59. Another way to see the problem is to note that the price of the item is 100% and you are adding an additional 6% so the final price is 106% of the cost, i.e. $1.50x1.06 = $1.59. In general if the cost is C and the final price is P then Cx1.06=P This is an equation that you want to solve for C, so C = P/1.06. In general if you want to 'work back' from the final price, you divide the final price by 100% plus the tax rate.
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Ultraglide
Advanced Member

Canada
299 Posts

Posted - 04/09/2011 :  12:28:02  Show Profile  Reply with Quote
One further note, this is what retailers do when they offer items with no sales tax. They actually adjust the price so that when the tax is added (because tax must be paid), you end up with the original price.
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Myke
New Member

USA
2 Posts

Posted - 04/09/2011 :  18:14:06  Show Profile  Reply with Quote
Thanks Ultraglide, I was able to understand and help my daughter understand. I'm fairly good at math, but I was stumped on this one.
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