2. Chapter 3
Decimals

3. 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

4. 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

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
$ >The 6 is in the hundredths place value
> The 5 is in the tenths place value
> The 4 is in the ten thousandths place value

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
.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 Fractions
545
Step 1
545 1
Step 2
.54 1 2
Places 3
Step 3
545
1000

13. Adding Decimals Add: 7 + 5.3 + 24.139 + .0003 + 5.02 7.0000 5.3000
.0003
5.0200

14. Subtracting Decimals
Subtract:
45.300
30.027

15. Multiplying Decimals 9.09 (2 decimal places) x 3.8 (1 decimal places)
34542
34.542
5 decimal places
17275
.17275
6.91 x

16. Dividing Decimals 3 Steps
1. Make the divisor a whole number by moving the decimal point to the right
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.
3. Place the decimal point in the quotient above the new decimal point in the dividend. Divide as usual.
Example
18.42 45
378
360
189
180 90

17. Decimals Applications in Foreign Currency
Key Currency Cross Rates
2 billion pounds x $ = $ = $3.49 Billion
Check $3.49 x = = 2 Billion pounds

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