Basic Mathematics for College Students

4.2 Adding and Subtracting Decimals 337

Solution

a.

The estimate is 690. If we compute , the sum is 694.7. We can

see that the estimate is close; it’s just 4.7 less than 694.7.

b.We use front-end rounding. Each number is rounded to its largest place value.

The estimate is 340. If we compute , the difference is 324.76. We

can see that the estimate is close; it’s 15.24 more than 324.76.

381.7757.01

Round to the nearest hundred.

Round to the nearest ten.

400

 60

340

381.77

 57.01

261.76432.94

Round to the nearest ten.

Round to the nearest ten.

260

 430

690

261.76

 432.94

5 Solve application problems by adding

and subtracting decimals.

To make a profit, a merchant must sell an item for more than she paid for it. The price
at which the merchant sells the product, called the retail price,is the sumof what the
item costthe merchant plus the markup.

Retail pricecostmarkup

EXAMPLE (^10) Pricing Find the retail price of a Rubik’s Cube if a game
store owner buys them for $8.95 each and then marks them up $4.25 to sell in her
store.
Analyze

• Rubik’s Cubes cost the store owner $8.95 each. Given


• She marks up the price $4.25. Given


• What is the retail price of a Rubik’s Cube? Find

Form We translate the words of the problem to numbers and symbols.

is equal to plus

The retail price  8.95  4.25

SolveUse vertical form to perform decimal addition:

StateThe retail price of a Rubik’s Cube is $13.20.

CheckWe can estimate to check the result. If we use $9 to approximate the cost
of a Rubik’s Cube to the store owner and $4 to be the approximate markup, then
the retail price is about $9$4$13. The result, $13.20, seems reasonable.

8

1

.9

1

5

 4.25

13.20

The retail price the cost the markup.

Self Check 10

PRICINGFind the retail price of a

wool coat if a clothing outlet

buys them for $109.95 each and

then marks them up $99.95 to

sell in its stores.

Now TryProblem 91

EXAMPLE (^11) Kitchen SinksOne model of kitchen sink is made of
18-gauge stainless steel that is 0.0500 inch thick. Another, less expensive, model is
made from 20-gauge stainless steel that is 0.0375 inch thick. How much thicker
is the 18-gauge?
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