4–5
Fractions and Decimals
EXAMPLES
MAIN IDEA • Write fractions as terminating or repeating decimals and write decimals as fractions.
Use Mental Math
Write each fraction or mixed number as a decimal. 9 _ 10 × 10
THINK
9 _ = 10
90 _ 100
× 10
9 So, _ = 10
0.9 .
3 7_ 5
3 7_ =7+ 5
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
=7+
_3 5
0.6
= 7.6 3 So, 7 _ = 5
Think of it as a sum. 3 You know that _ = 0.6. 5
Add mentally.
7.6 .
Check Your Progress Write each fraction or mixed number as a decimal. ®
ORGANIZE IT Under the tab for Lesson 4-5, take notes on writing fractions as decimals and writing decimals as fractions. Include examples. iV>Ã] À>VÌÃÊ ViÌà >`Ê*iÀ Àâ>Ì {£Ê*ÀiÊ>VÌ ÌÀà ÃÌÊ Ê>V {ÓÊÀi>Ìi À}>âi`Ê ÃÌ {ÎÊ >iÊ>Ê" ÊÀ>VÌà {{Ê-«vÞ} à > Ê iV Ê>` {xÊÀ>VÌà >`Ê*iÀViÌà {ÈÊÀ>VÌÃÊ `Ê iV>à {ÇÊ*iÀViÌÃÊ> Ì«i Ê Õ {nÊ i>ÃÌÊ
7 a. _ 25
0.28
1 b. 9 _ 5
9.2
à Ì>Ê ÕLiÀ `Ê"À`iÀ}Ê,>
{Ê «>À}Ê>
Math Connects, Course 2
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4–5 EXAMPLE
Use Pencil and Paper or a Calculator
1 Write _ as a decimal. 8
METHOD 1 Use paper and pencil. 0.125 8 """"""""""""""""""""""""" 1.000 8 __ 20 - 16 ___ 40 40 ___ 0
Divide
1 by 8 .
Division ends when the remainder is 0.
WRITE IT
METHOD 2 Use a calculator.
Write the following
1 8
decimal equivalents: 1 _ _1 , _1 , _2 , _1 , _3 , _1 , _ , 1.
ENTER
1 So, _ = 8
0.125
0.125
.
2 3 3 4 4 5 10 8
Check Your Progress Write each fraction or mixed number as a decimal. 2 a. _ 5
0.4
20
1.35
BUILD YOUR VOCABULARY (pages 77–78) A terminating decimal is a decimal whose digits
end
Repeating decimals have a pattern in the digits that repeats
forever .
Bar notation is used to indicate that a number repeats forever by writing a that repeat.
88
Math Connects, Course 2
bar
over the
digits
.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
7 b. 1 _
4–5 EXAMPLES
Write Fractions as Repeating Decimals
1 Write _ as a decimal. (parallels Example 5 in text) 11
METHOD 1 Use paper and pencil. 0.0909... 11 """""""""""""""""""""""""""""" 1.0000 0 __ 100
99
____ 10 0 __
100 99 ____
1 METHOD 2 Use a calculator. 1 11
ENTER
0.0909...
−− 1 = 0.09 . So, _ 11
5 Check Your Progress Write 2 _ as a decimal. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
11
−− 2.45
EXAMPLE
Use a Power of 10 (parallels Example 6 in text)
CEREAL Jorge read that 0.72 of his favorite cereal was whole-grain wheat. Find what fraction of his cereal, in simplest form, is whole-grain wheat. 72 0.72 = _ 100
18 =_ 25
HOMEWORK ASSIGNMENT Page(s): Exercises:
So,
18 _ 25
The final digit,
2 , is in the hundredths place.
Simplify. of the cereal is whole-grain wheat.
Check Your Progress EXERCISE Jeanette ran 0.86 of a mile. What fraction of a mile did she run?
43 _ 50
Math Connects, Course 2
89
