Chapter 7: Ratios, Proportions, and Percentages 95When you go out shopping, you don’t always know exactly what the sales tax is. If you buy
a jacket with a price tag that says it costs $78.95, and the cashier asks you for $83.81, you can
subtract 83.81 – 78.95 = 4.86 and know that you paid $4.86 in sales tax. But what is the tax rate?
Sales tax = rate v amount of the sale, so the rate will equal the sales tax divided by the amount
of the sale. Take the $4.86 you paid in tax and divide by the $78.95 cost of the jacket.
4.86 z 78.95 } 0.0616 , or 6 .16%.MATH TRAP
The amount you pay in tax on a sale is not always just the state sales tax. Many cities
add their own sales tax in addition to the state sales tax. The city sales tax will also be
a percent of your purchase, but because both are added on to your bill, you may not
be able to tell how much went to the city and how much to the state.Calculating Tips
In many U.S. restaurants, the staff who serve the customers’ meals are paid a lower than usual
wage and depend on tips to make up the rest of their income. Tipping began as a way to reward
excellent service but has become an expected addition to the bill in many restaurants. So the
question becomes, “How much should I tip?” Usually, the recommendation is that you tip your
server a percentage of the bill for the meal. The recommended percent varies by region, by the
type of restaurant, and by the quality of service, but is usually in the range of 15 to 20 percent.
If you and a friend have lunch at a restaurant, and the bill for your food and drinks totals $27.46,
how much of a tip should you leave for your server?
If you feel that 15 percent is appropriate, you would multiply the bill amount by 0.15. 27.46 v 0.15
takes a bit of work, but it equals $4.12. If you’d rather leave a 20 percent tip, multiply 27.46 v 0.20,
and the tip will be $5.49. With that information in hand, you can decide to leave somewhere
between $4 and $5.50. Most people won’t worry about the pennies and will figure the tip based
on the whole dollar amount.WORLDLY WISDOM
People who know the sales tax rate in their area often use the tax to help them
calculate the tip. If you know your sales tax is 5 percent of the bill, you can look at
your check to see what the tax amount is. If you want to tip 15 percent, triple the
tax. If you want to tip 20 percent, multiply the tax by 4. A tax rate of approximately
6 percent is fairly common, and many people triple the tax to get 18 percent of the
bill. That’s nicely in the 15 to 20 percent range.