Basic Mathematics for College Students

6.3 Applications of Percent 537

EXAMPLE (^2) Total Cost Find the total
cost of the child’s car seat shown on the right if
the sales tax rate is 7.2%.
StrategyFirst, we will find the sales tax on the
child’s car seat.
WHYThen we can add the purchase price and
the sales tax to find the total of the car seat.
SolutionThe sales tax rate is 7.2% and the
purchase price is $249.50.
This is the sales tax formula.
Substitute 7.2% for the sales tax rate
and $249.50 for the purchase price.
Write 7.2% as a decimal: 7.2% 0.072.
Do the multiplication.
The rounding digit in the hundredths column is 6.
Prepare to round the sales tax to the
nearest cent (hundredth) by identifying
the rounding digit and test digit.
The test digit is 4.
Since the test digit is less than 5, round down.
Thus, the sales tax on the $249.50 purchase is $17.96. The total cost of the car seat
is the sum of its purchase price and the sales tax.
This is the formula for
the total cost.
Substitute $249.50 for the purchase
price and $17.96 for the sales tax.
$267.46 Do the addition.

$249.50$17.96

Total costpurchase pricesales tax

$17.96

$17.964

$17.964

0.072#$249.50

 7.2%  $249.50

Sales taxsales tax ratepurchase price

Self Check 2

TOTAL COSTFind the total cost of

a $179.95 baby stroller if the

sales tax rate on the purchase is

3.2%.

Now TryProblem 17

Child’s

Car

Seat

$249.50

Buy today!

Ships next business day

Saftey-T First

249.50

0.072

49900

1746500

17.96400

249

1

.50

 17.96

267.46

EXAMPLE (^3) Withholding Tax A waitress found that $11.04 was
deducted from her weekly gross earnings of $240 for federal income tax. What
withholding tax rate was used?
StrategyWe will carefully read the problem and use the given facts to write them
in the form of a percent sentence.
WHYThen we can translate the sentence into a percent equation (or percent
proportion) and solve it to find the unknown withholding tax rate.
SolutionThere are two methods that can be used to solve this problem.
The percent equation method:Since the withholding tax of $11.04 is some unknown
percent of her weekly gross earnings of $240, the percent sentence is:
is of
11.04  x  240 This is the percent equation to solve.
$11.04 what percent $240?
Self Check 3
INHERITANCE TAXA tax of $5,250
was paid on an inheritance of
$15,000. What was the inheritance
tax rate?
Now TryProblem 21
In addition to sales tax, we pay many other taxes in our daily lives. Income tax,
gasoline tax, and Social Security tax are just a few. To find such tax rates, we can use an
approach like that discussed in Section 6.2.