Basic Mathematics for College Students

4.3 Multiplying Decimals 353

SolveWe will use the rule for the order of operations to evaluate the expression:

Do the multiplication first.

Do the addition.

StateThe cashier will earn a total of $641.90 for the week.

CheckWe can use estimation to check. The cashier works 40 hours per week for
approximately $13 per hour to earn about. His 6 hours of overtime
at approximately $20 per hour earns him about. His total earnings
that week are about $520$120$640. The result, $641.90, seems reasonable.

6 $20$120

40 $13$520

641.90

40 13.10 6 19.65524.00117.90

1.11.61 2.0.00144 3.836.6 4. a.72.1 b.6,080 5. a.12.99 b.0.00000002

6. a.567,100,000 b.50,820,000,000 c.4,133,000,000,000 7. a.36.3 b.4,496.8


7. a.1.69 b.0.0081 9.1.76 10.110.214 11. a. 280 b.35.96 c.789.9
   12.78 mm 13.$731.40

ANSWERS TO SELF CHECKS

SECTION 4.3 STUDY SET

VOCABULARY

Fill in the blanks.

1. In the multiplication problem shown below,
   label each factor,the partial products,and the
   product.


2. Numbers such as 10, 100, and 1,000 are called
   of 10.

CONCEPTS

Fill in the blanks.

3. Insert a decimal point in the correct place for each
   product shown below. Write placeholder zeros, if
   necessary.
   a. b.

3.4

 2.6

204

680

8.84

13.10

 40

0000

5240

524.00

1

5

9

3

.6

3

5

 6

117.90

52

1

4.00

 117.90

641.90

3.8

0.6

228

1.79

 8.1

179

14320

14499











c. d.

4. Fill in the blanks.
   a. To find the product of a decimal and 10, 100, 1,000,
   and so on, move the decimal point to the
   the same number of places as there are zeros in
   the power of 10.
   b. To find the product of a decimal and 0.1, 0.01,
   0.001, and so on, move the decimal point to the
   the same number of places as there are in
   the power of 10.


5. Determine whether the signof each result is positive
   or negative.You do not have to find the product.
   a.
   b.


6. a.When we move its decimal point to the right, does
   a decimal number get larger or smaller?
   b. When we move its decimal point to the left, does a
   decimal number get larger or smaller?

NOTATION

7. a.List the first five powers of 10 that are greater
   than 1.
   b. List the first five powers of 10 that are less than 1.

4.092.274

7.6(1.8)

0.013

 0.02

0026

2.0

 7

140