1. Chapter 3 Decimals McGraw-Hill/Irwin
©2011 The McGraw-Hill Companies, All Rights Reserved

2. Learning Unit Objectives#3
Decimals
Learning Unit Objectives
Rounding Decimals; Fraction and Decimal Conversions
LU3.1
Explain the place values of whole numbers and decimals; round decimals
Convert decimal fractions to decimals, proper fractions to decimals, mixed numbers to decimals, and pure and mixed decimals to decimal fractions
3-2

3. Learning Unit Objectives#3
Decimals
Learning Unit Objectives
Adding, Subtracting, Multiplying, and Dividing Decimals
LU3.2
Add, subtract, multiply, and divide decimals
Multiply and divide decimals by shortcut methods
Complete decimal applications in foreign currency
3-3

4. Table 3.1 - Bag of M&M’s Decimal Percent
Color Fraction (hundredth) (hundredth)
Yellow % 55
Red %
Blue %
Orange %
Brown %
Green %
Total %
55 = 1

5. Decimal place-value chart
Figure 3.1
Whole Number Groups
Decimal Place Values
Hundredths
Ten Thousandths
Thousands
Hundreds
Tens
Ones
Decimal Point
Tenths
Thousandths
Hundred Thousandths 1 10
1 .
100
1 .
1,000
10,000
100,000
1,000
100 10 1
and

6. Rounding Decimals .3272727 .337272 .33 Step 1. Identify the place
value of the digit you want
to round
Step 3. Drop all digits to the right
of the identified digit
Step 2. Identify the digit to the right.
If 5 or more, increase the identified digit
by 1. If less than 5 do not change
.33

7. Rounding Decimals Round to nearest dollar: $166.39 $166
Round to nearest cent: $1, $1,196.89
Round to nearest hundredth: $ $38.56
Round to nearest thousandth: $1, $1,

8. Converting Decimal Fractions to Decimals
2 Steps
1. Count the number of zeros in the denominator.
2. Place the numerator of the decimal fraction to the right of the decimal point the same number of places as you have zeros in the denominator. Do not go over the total number of denominator zeros.
Fraction Decimal # of places 10
100
1,000
10,000

9. Converting Proper Fractions to Decimals
.75
2.8 20
EQUALS 3 4
Step 1
.75

10. Converting Mixed Numbers to Decimals.4
2.0
(Step 1) 2 5 8
(Step 2)
8.4

11. Converting Pure Decimals to Decimal Fractions
Step 1 24
Step 2 24 1
.24
Places 2
Step 3 24
100

12. Converting Mixed Decimals to Decimal Fractions45
Step 1 45 1
Step 2
17.45
Places 2
Step 3
=17

13. Adding Decimals Add: 4 + 7.3 + 36.139 + .0007 + 8.22 4.0000 7.3000
.0007
8.2200

14. Subtracting Decimals
Subtract:
45.300
30.027

15. Multiplying Decimals 8.52 (2 decimal places) x 6.7 (1 decimal places)
57084
57.084
5 decimal places
3776
.03776
Need to add zero
2.36 x

16. Dividing Decimals
Step 1. Make the divisor a whole number by moving the decimal point to the right
Step 2. Move the decimal point in the dividend to the right the same number of places as in step 1. If there are not enough places, add zeros to the right of the dividend.
Step 3. Place the decimal point in the quotient above the new decimal point in the dividend. Divide as usual.
Example
13.12 25 78 75 30 50

17. Decimals Applications in Foreign Currency
The Wall Street Journal clip shows in China the price of Microsoft Office was reduced to 199 yuan from an original price of 699 yuan. Using the currencies table lets us see what the original as well as sales price is in U.S. dollars. In the table on page 74 1 yuan equals $ To find the original selling price you multiply the number of yuan (699) times $.1463.
699 yuan x $.1463 = $102.26
The original selling price in U.S. Dollars is $ To find the new selling price in U.S. dollars, you multiply the number of yuan 199 times $ The new selling price in U.S. dollars is $29.11.
$199 x $.1463 = $29.11
Table factor from currency table on page 74
Check $29.11 x = yuan
Each 1 equal yuan

18. Shortcuts for Multiples of 10
Multiplication
Count the zeros in the multiplier
Move the decimal point the same
number of spaces to the right
6890
6.89 x 1000
68.9
6.89 x 10
6.89 x 100
689

19. Shortcuts for Multiples of 10
Division
Count the zeros in the divisor
Move the decimal point the same
number of spaces to the left
.00689
.689
6.89 / 1000
6.89 / 10
6.89 / 100
.0689