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Chapter 3
Decimals
Prepared by Dr. Elena Skliarenko
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McGraw-Hill Companies. All rights reserved.
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#3
LU3.1
Fractions
Learning Unit Objectives
Rounding Decimals; Fractions &
Decimal Conversions
•
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
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McGraw-Hill Companies. All rights reserved.
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#3
LU3.2
Fractions
Learning Unit Objectives
Adding, Subtracting, Dividing, and
Multiplying Decimals
•
Add, subtract, multiply, and divide decimals
•
Multiply and divide decimals by shortcut methods
•
Complete decimal applications in foreign currency
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#3
LU3.3
Fractions
Learning Unit Objectives
Using a Calculator to perform
operations with Decimals
•
Converting fractions to decimals and decimals
to fractions
•
Adding, subtracting, multiplying, and dividing
decimals
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Decimal place-value chart
and
1
10
1 .
100
1 .
1,000
1 .
10,000
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Hundred
Thousandths
1
Ten Thousandths
Ones
10
Thousandths
Tens
100
Hundredths
Hundreds
1,000
Tenths
Thousands
Figure 3.1
1 .
100,000
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Rounding Decimals
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
.3272727
.337272
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
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7
Converting Proper Fractions to
Decimals .75
4 3.00
2.8
20
20
0
3
4
.75
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Converting Pure Decimals to Decimal
Fractions
Step 1
Step 2
.24
Places
Step 3
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24
1
2
24
100
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Converting Mixed Decimals to Decimal
Fractions
Step 1
.54
1
2
Step 2
Places
Step 3
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545
545
1
3
545
1000
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Adding and Subtracting Decimals
Add: 7 + 5.3 + 24.139 + .0003 + 5.02
7.0000
5.3000
24.1390
.0003
5.0200
41.4593
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Multiplying Decimals
9.09
x 3.8
34542
17275
3 decimal places
5 decimal places
34.542
.17275
6.91
x .025
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Dividing Decimals
Question
3 Steps
4.5 82.89
•Make the divisor a whole
number by moving the decimal
point to the right
•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.
•Place the decimal point in the
quotient above the new decimal
point in the dividend. Divide as
usual.
Answer
45. 828.9
18.42
45. 828.90
45
378
360
189
180
90
90
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Decimals Applications in Foreign Currency
Key Currency Cross Rates
US$
Yen
Euro
C$
U.K.
Aust $
Sfranc
US $
1
122
1.002
1.558
0.64
1.784
1.464
Yen
0.008199
1
0.008213
0.01277
0.005249
0.01463
0.012
Euro
0.9983
121.8
1
1.555
0.6391
1.781
1.462
C$
U.K.Pound Aust $
Sfranc
0.6418
1.562
0.5606
6831
78.28
190.5
68.37
83.31
0.6429
1.565
0.5616
0.6842
1
2.434
0.8734
1.064
0.4109
1
0.3589 0.4373
1.145
2.786 1
1.218
0.9397 2.287
0.8207
1
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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
6.89 x 10
68.9
6.89 x 100
689
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Shortcuts for Multiples of 10
Division
•Count the zeros in the divisor
•Move the decimal point the same
number of spaces to the right
.00689
6.89 / 1000
6.89 / 10
.689
6.89 / 100
.0689
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Proper use of the calculator
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Converting mixed numbers to decimals
and decimals to mixed numbers a b/c
For example , to convert 1 ¾ into decimal you have to follow these steps.
Step 1. Enter 1 ¾ in your calculator
1 a b/c 3 a b/c 4  1 r 3 r 4
Step 2. Press equal sign button =
Step 3. Press the “magic” button a b/c  1.75
To convert decimal number into mixed number or fraction undertake the following
steps:
Step 1. Enter decimal number in your calculator
Step 2. Press equal sign button
Step 3. Press the “magic” button a b/c
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