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📚 Prealgebra 2e
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4.1 Visualize Fractions

Understand the Meaning of Fractions

Andy and Bobby love pizza. On Monday night, they share a pizza equally. How much of the pizza does each one get? Are you thinking that each boy gets half of the pizza? That’s right. There is one whole pizza, evenly divided into two parts, so each boy gets one of the two equal parts.

In math, we write 12 to mean one out of two parts.

An image of a round pizza sliced vertically down the center, creating two equal pieces. Each piece is labeled as one half.

On Tuesday, Andy and Bobby share a pizza with their parents, Fred and Christy, with each person getting an equal amount of the whole pizza. How much of the pizza does each person get? There is one whole pizza, divided evenly into four equal parts. Each person has one of the four equal parts, so each has 14 of the pizza.

An image of a round pizza sliced vertically and horizontally, creating four equal pieces. Each piece is labeled as one fourth.

On Wednesday, the family invites some friends over for a pizza dinner. There are a total of 12 people. If they share the pizza equally, each person would get 112 of the pizza.

An image of a round pizza sliced into twelve equal wedges. Each piece is labeled as one twelfth.

A fraction is a way to represent parts of a whole. The denominator b represents the number of equal parts the whole has been divided into, and the numerator a represents how many parts are included. The denominator, b, cannot equal zero because division by zero is undefined.

In Figure 4.2, the circle has been divided into three parts of equal size. Each part represents 13 of the circle. This type of model is called a fraction circle. Other shapes, such as rectangles, can also be used to model fractions.

A circle is divided into three equal wedges. Each piece is labeled as one third.
Figure 4.2

What does the fraction 23 represent? The fraction 23 means two of three equal parts.

A circle is divided into three equal wedges. Two of the wedges are shaded.

In Example 1 and Example 2, we used circles and rectangles to model fractions. Fractions can also be modeled as manipulatives called fraction tiles, as shown in Figure 4.3. Here, the whole is modeled as one long, undivided rectangular tile. Beneath it are tiles of equal length divided into different numbers of equally sized parts.

One long, undivided rectangular tile is shown, labeled “1”. Below it is a rectangular tile of the same size and shape that has been divided vertically into two equal pieces, each labeled as one half. Below that is another rectangular tile that has been divided into three equal pieces, each labeled as one third. Below that is another rectangular tile that has been divided into four equal pieces, each labeled as one fourth. Below that is another rectangular tile that has been divided into six pieces, each labeled as one sixth.
Figure 4.3

We’ll be using fraction tiles to discover some basic facts about fractions. Refer to Figure 4.3 to answer the following questions:

How many 12 tiles does it take to make one whole tile?It takes two halves to make a whole, so two out of two is 22=1.
How many 13 tiles does it take to make one whole tile?It takes three thirds, so three out of three is 33=1.
How many 14 tiles does it take to make one whole tile?It takes four fourths, so four out of four is 44=1.
How many 16 tiles does it take to make one whole tile?It takes six sixths, so six out of six is 66=1.
What if the whole were divided into 24 equal parts? (We have not shown fraction tiles to represent this, but try to visualize it in your mind.) How many 124 tiles does it take to make one whole tile?It takes 24 twenty-fourths, so 2424=1.

It takes 24 twenty-fourths, so 2424=1.

This leads us to the Property of One.

What if we have more fraction pieces than we need for 1 whole? We’ll look at this in the next example.

Model Improper Fractions and Mixed Numbers

In Example 4 (b), you had eight equal fifth pieces. You used five of them to make one whole, and you had three fifths left over. Let us use fraction notation to show what happened. You had eight pieces, each of them one fifth, 15, so altogether you had eight fifths, which we can write as 85. The fraction 85 is one whole, 1, plus three fifths, 35, or 135, which is read as one and three-fifths.

The number 135 is called a mixed number. A mixed number consists of a whole number and a fraction.

Fractions such as 54,32,55, and 73 are called improper fractions. In an improper fraction, the numerator is greater than or equal to the denominator, so its value is greater than or equal to one. When a fraction has a numerator that is smaller than the denominator, it is called a proper fraction, and its value is less than one. Fractions such as 12,37, and 1118 are proper fractions.

Convert between Improper Fractions and Mixed Numbers

In Example 7, we converted the improper fraction 116 to the mixed number 156 using fraction circles. We did this by grouping six sixths together to make a whole; then we looked to see how many of the 11 pieces were left. We saw that 116 made one whole group of six sixths plus five more sixths, showing that 116=156.

The division expression 116 (which can also be written as 611) tells us to find how many groups of 6 are in 11. To convert an improper fraction to a mixed number without fraction circles, we divide.

In Example 8, we changed 145 to an improper fraction by first seeing that the whole is a set of five fifths. So we had five fifths and four more fifths.

55+45=95

Where did the nine come from? There are nine fifths—one whole (five fifths) plus four fifths. Let us use this idea to see how to convert a mixed number to an improper fraction.

Model Equivalent Fractions

Let’s think about Andy and Bobby and their favorite food again. If Andy eats 12 of a pizza and Bobby eats 24 of the pizza, have they eaten the same amount of pizza? In other words, does 12=24? We can use fraction tiles to find out whether Andy and Bobby have eaten equivalent parts of the pizza.

Fraction tiles serve as a useful model of equivalent fractions. You may want to use fraction tiles to do the following activity. Or you might make a copy of Figure 4.3 and extend it to include eighths, tenths, and twelfths.

Start with a 12 tile. How many fourths equal one-half? How many of the 14 tiles exactly cover the 12 tile?

One long, undivided rectangle is shown. Below it is a rectangle divided vertically into two pieces, each labeled as one half. Below that is a rectangle divided vertically into four pieces, each labeled as one fourth.

Since two 14 tiles cover the 12 tile, we see that 24 is the same as 12, or 24=12.

How many of the 16 tiles cover the 12 tile?

One long, undivided rectangle is shown. Below it is a rectangle divided vertically into two pieces, each labeled as one half. Below that is a rectangle divided vertically into six pieces, each labeled as one sixth.

Since three 16 tiles cover the 12 tile, we see that 36 is the same as 12.

So, 36=12. The fractions are equivalent fractions.

Find Equivalent Fractions

We used fraction tiles to show that there are many fractions equivalent to 12. For example, 24,36, and 48 are all equivalent to 12. When we lined up the fraction tiles, it took four of the 18 tiles to make the same length as a 12 tile. This showed that 48=12. See Example 13.

We can show this with pizzas, too. Figure 4.4(a) shows a single pizza, cut into two equal pieces with 12 shaded. Figure 4.4(b) shows a second pizza of the same size, cut into eight pieces with 48 shaded.

Two pizzas are shown. The pizza on the left is divided into 2 equal pieces. 1 piece is shaded. The pizza on the right is divided into 8 equal pieces. 4 pieces are shaded.
Figure 4.4

This is another way to show that 12 is equivalent to 48.

How can we use mathematics to change 12 into 48? How could you take a pizza that is cut into two pieces and cut it into eight pieces? You could cut each of the two larger pieces into four smaller pieces! The whole pizza would then be cut into eight pieces instead of just two. Mathematically, what we’ve described could be written as:

1 times 4 over 2 times 4 is written with the 4s in red. This is set equal to 4 over 8.

These models lead to the Equivalent Fractions Property, which states that if we multiply the numerator and denominator of a fraction by the same number, the value of the fraction does not change.

When working with fractions, it is often necessary to express the same fraction in different forms. To find equivalent forms of a fraction, we can use the Equivalent Fractions Property. For example, consider the fraction one-half.

The top line says that 1 times 3 over 2 times 3 equals 3 over 6, so one half equals 3 sixths. The next line says that 1 times 2 over 2 times 2 equals 2 over 4, so one half equals 2 fourths. The last line says that 1 times 10 over 2 times 10 equals 10 over 20, so one half equals 10 twentieths.

So, we say that 12,24,36, and 1020 are equivalent fractions.

Locate Fractions and Mixed Numbers on the Number Line

Now we are ready to plot fractions on a number line. This will help us visualize fractions and understand their values.

Let us locate 15,45,3,313,74,92,5, and 83 on the number line.

We will start with the whole numbers 3 and 5 because they are the easiest to plot.

A number line is shown with the numbers 3, 4, and 5. There are red dots at 3 and at 5.

The proper fractions listed are 15 and 45. We know proper fractions have values less than one, so 15 and 45 are located between the whole numbers 0 and 1. The denominators are both 5, so we need to divide the segment of the number line between 0 and 1 into five equal parts. We can do this by drawing four equally spaced marks on the number line, which we can then label as 15,25,35, and 45.

Now plot points at 15 and 45.

A number line is shown. It shows 0, 1 fifth, 2 fifths, 3 fifths, 4 fifths, and 1. There are red dots at 1 fifth and at 4 fifths.

The only mixed number to plot is 313. Between what two whole numbers is 313? Remember that a mixed number is a whole number plus a proper fraction, so 313>3. Since it is greater than 3, but not a whole unit greater, 313 is between 3 and 4. We need to divide the portion of the number line between 3 and 4 into three equal pieces (thirds) and plot 313 at the first mark.

A number line is shown with whole number 0 through 5. Between 3 and 4, 3 and 1 third and 3 and 2 thirds are labeled. There is a red dot at 3 and 1 third.

Finally, look at the improper fractions 74,92, and 83. Locating these points will be easier if you change each of them to a mixed number.

74=134,92=412,83=223

Here is the number line with all the points plotted.

A number line is shown with whole numbers 0 through 6. Between 0 and 1, 1 fifth and 4 fifths are labeled and shown with red dots. Between 1 and 2, 7 fourths is labeled and shown with a red dot. Between 2 and 3, 8 thirds is labeled and shown with a red dot. Between 3 and 4, 3 and 1 third is labeled and shown with a red dot. Between 4 and 5, 9 halves is labeled and shown with a red dot.

In Introduction to Integers, we defined the opposite of a number. It is the number that is the same distance from zero on the number line but on the opposite side of zero. We saw, for example, that the opposite of 7 is −7 and the opposite of −7 is 7.

A number line is shown. It shows the numbers negative 7, 0 and 7. There are red dots at negative 7 and 7. The space between negative 7 and 0 is labeled as 7 units. The space between 0 and 7 is labeled as 7 units.

Fractions have opposites, too. The opposite of 34 is 34. It is the same distance from 0 on the number line, but on the opposite side of 0.

A number line is shown. It shows the numbers negative 1, negative 3 fourths, 0, 3 fourths, and 1. There are red dots at negative 3 fourths and 3 fourths. The space between negative 3 fourths and 0 is labeled as 3 fourths of a unit. The space between 0 and 3 fourths is labeled as 3 fourths of a unit.

Thinking of negative fractions as the opposite of positive fractions will help us locate them on the number line. To locate 158 on the number line, first think of where 158 is located. It is an improper fraction, so we first convert it to the mixed number 178 and see that it will be between 1 and 2 on the number line. So its opposite, 158, will be between −1 and −2 on the number line.

A number line is shown. It shows the numbers negative 2, negative 1, 0, 1, and 2. Between negative 2 and negative 1, negative 1 and 7 eighths is labeled and marked with a red dot. The distance between negative 1 and 7 eighths and 0 is marked as 15 eighths units. Between 1 and 2, 1 and 7 eighths is labeled and marked with a red dot. The distance between 0 and 1 and 7 eighths is marked as 15 eighths units.

Order Fractions and Mixed Numbers

We can use the inequality symbols to order fractions. Remember that a>b means that a is to the right of b on the number line. As we move from left to right on a number line, the values increase.

Key Concepts

  • Property of One
    • Any number, except zero, divided by itself is one.
      aa=1, where a0.
  • Mixed Numbers
    • A mixed number consists of a whole number a and a fraction bc where c0.
    • It is written as follows: abcc0
  • Proper and Improper Fractions
    • The fraction ab is a proper fraction if a<b and an improper fraction if ab.
  • Convert an improper fraction to a mixed number.
    1. Divide the denominator into the numerator.
    2. Identify the quotient, remainder, and divisor.
    3. Write the mixed number as quotientremainderdivisor.
  • Convert a mixed number to an improper fraction.
    1. Multiply the whole number by the denominator.
    2. Add the numerator to the product found in Step 1.
    3. Write the final sum over the original denominator.
  • Equivalent Fractions Property
    • If a, b, and c are numbers where b0, c0, then ab=acbc.

Practice Makes Perfect

In the following exercises, name the fraction of each figure that is shaded.

In part “a”, a circle is divided into 4 equal pieces. 1 piece is shaded. In part “b”, a circle is divided into 4 equal pieces. 3 pieces are shaded. In part “c”, a circle is divided into 8 equal pieces. 3 pieces are shaded. In part “d”, a circle is divided into 8 equal pieces. 5 pieces are shaded.
  1. 14
  2. 34
  3. 38
  4. 58
In part “a”, a circle is divided into 12 equal pieces. 7 pieces are shaded. In part “b”, a circle is divided into 12 equal pieces. 5 pieces are shaded. In part “c”, a square is divided into 9 equal pieces. 4 of the pieces are shaded. In part “d”, a square is divided into 9 equal pieces. 5 pieces are shaded.

In the following exercises, shade parts of circles or squares to model the following fractions.

12

A circle is shown. It is divided into 2 equal pieces. 1 piece is shaded.

13

34

A circle is shown. It is divided into 4 equal pieces. 3 pieces are shaded.

25

56

A circle is shown. It is divided into 6 equal pieces. 5 pieces are shaded.

78

58

A circle is shown. It is divided into 8 equal pieces. 5 pieces are shaded.

710

In the following exercises, use fraction circles to make wholes using the following pieces.

3 thirds

A circle is shown. It is divided into 3 equal pieces. All 3 pieces are shaded.

8 eighths

7 sixths

Two circles are shown. Each is divided into 6 equal pieces. All 6 pieces are shaded in the circle on the left. 1 piece is shaded in the circle on the right.

4 thirds

7 fifths

Two circles are shown. Each is divided into 5 equal pieces. All 5 pieces are shaded in the circle on the left. 2 pieces are shaded in the circle on the right.

7 fourths

In the following exercises, name the improper fractions. Then write each improper fraction as a mixed number.

In part “a”, two circles are shown. Each is divided into 4 equal pieces. The circle on the left has all 4 pieces shaded. The circle on the right has 1 piece shaded. In part “b”, two circles are shown. Each is divided into 4 equal pieces. The circle on the left has all 4 pieces shaded. The circle on the right has 3 pieces shaded. In part “c”, two circles are shown. Each is divided into 8 equal pieces. The circle on the left has all 8 pieces shaded. The circle on the right has 3 pieces shaded.
  1. 54=114
  2. 74=134
  3. 118=138
In part “a”, 2 circles are shown. Each is divided into 8 equal pieces. The circle on the left has all 8 pieces shaded. The circle on the right has 1 piece shaded. In part “b”, two squares are shown. Each is divided into 4 equal pieces. The square on the left has all 4 pieces shaded. The circle on the right has 1 piece shaded. In part “c”, two squares are shown. Each is divided into 9 equal pieces. The square on the left has all 9 pieces shaded. The square on the right has 2 pieces shaded.
In part “a”, 3 circles are shown. Each is divided into 4 equal pieces. The first two circles have all 4 pieces shaded. The third circle has 3 pieces shaded. In part “b”, 3 circles are shown. Each is divided into 8 equal pieces. The first two circles have all 8 pieces shaded. The third circle has 3 pieces shaded.
  1. 114=234
  2. 198=238

In the following exercises, draw fraction circles to model the given fraction.

33

44

A circle is shown. It is divided into 4 equal pieces. All 4 pieces are shaded.

74

53

Two circles are shown. Each is divided into 3 equal pieces. All 3 pieces are shaded in the circle on the left. 2 pieces are shaded in the circle on the right.

116

138

Two circles are shown. Each is divided into 8 equal pieces. All 8 pieces are shaded in the circle on the left. 5 pieces are shaded in the circle on the right.

103

94

Three circles are shown. Each is divided into 4 equal pieces. All 4 pieces are shaded in the two circles on the left. 1 piece is shaded in the circle on the right.

In the following exercises, rewrite the improper fraction as a mixed number.

32

53

123

114

135

235

256

289

319

4213

4715

3215

In the following exercises, rewrite the mixed number as an improper fraction.

123

125

75

214

256

176

279

257

197

347

359

329

In the following exercises, use fraction tiles or draw a figure to find equivalent fractions.

How many sixths equal one-third?

How many twelfths equal one-third?

4

How many eighths equal three-fourths?

How many twelfths equal three-fourths?

9

How many fourths equal three-halves?

How many sixths equal three-halves?

9

In the following exercises, find three fractions equivalent to the given fraction. Show your work, using figures or algebra.

14

13

Answers may vary. Correct answers include 26,39,412.

38

56

Answers may vary. Correct answers include 1012,1518,2024.

27

59

Answers may vary. Correct answers include 1018,1527,2036.

In the following exercises, plot the numbers on a number line.

23,54,125

13,74,135

A number line is shown. The numbers 0, 1, 2, 3, 4, 5, and 6 are labeled. Between 0 and 1, 1 third is labeled and shown with a red dot. Between 1 and 2, 7 fourths is labeled and shown with a red dot. Between 2 and 3, 13 fifths is labeled and shown with a red dot.

14,95,113

710,52,138,3

A number line is shown. The numbers 0, 1, 2, 3, 4, 5, and 6 are labeled. Between 0 and 1, 7 tenths is labeled and shown with a red dot. Between 1 and 2, 13 eighths is labeled and shown with a red dot. Between 2 and 3, 5 halves is labeled and shown with a red dot. 3 is labeled and shown with a red dot.

213,−213

134,−135

A number line is shown. The numbers negative 4, negative 3, negative 2, negative 1, 0, 1, 2, 3, and 4 are labeled. Between negative 3 and negative 2, negative 2 and 1 third is labeled and shown with a red dot. Between 2 and 3, 2 and 1 third is labeled and shown with a red dot.

34,34,123,−123,52,52

25,25,134,−134,83,83

A number line is shown. The numbers negative 4, negative 3, negative 2, negative 1, 0, 1, 2, 3, and 4 are labeled. Between negative 3 and negative 2, negative 8 thirds is labeled and shown with a red dot. Between negative 2 and negative 1, negative 1 and 3 fourths is labeled and shown with a red dot. Between negative 1 and 0, negative 2 fifths is labeled and shown with a red dot. Between 0 and 1, 2 fifths is labeled and shown with a red dot. Between 1 and 2, 1 and 3 fourths is labeled and shown with a red dot. Between 2 and 3, 8 thirds is labeled and shown with a red dot.

In the following exercises, order each of the following pairs of numbers, using < or >.

−1__14

−1__13

<

−212__3

−134__2

>

512__712

910__310

<

−3__135

−4__236

<

Everyday Math

Music Measures A choreographed dance is broken into counts. A 11 count has one step in a count, a 12 count has two steps in a count and a 13 count has three steps in a count. How many steps would be in a 15 count? What type of count has four steps in it?

Music Measures Fractions are used often in music. In 44 time, there are four quarter notes in one measure.

  1. ⓐ How many measures would eight quarter notes make?
  2. ⓑ The song “Happy Birthday to You” has 25 quarter notes. How many measures are there in “Happy Birthday to You?”
  1. ⓐ 2
  2. 614

Baking Nina is making five pans of fudge to serve after a music recital. For each pan, she needs 12 cup of walnuts.

  1. ⓐ How many cups of walnuts does she need for five pans of fudge?
  2. ⓑ Do you think it is easier to measure this amount when you use an improper fraction or a mixed number? Why?

Writing Exercises

Give an example from your life experience (outside of school) where it was important to understand fractions.

Answers will vary.

Explain how you locate the improper fraction 214 on a number line on which only the whole numbers from 0 through 10 are marked.

Self Check

ⓐ After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This table helps students assess their fraction knowledge across topics like understanding, modeling, converting, locating, and ordering fractions, with options for confident, some help, or not getting it.
Figure 4.5

ⓑ If most of your checks were:

…confidently. Congratulations! You have achieved the objectives in this section. Reflect on the study skills you used so that you can continue to use them. What did you do to become confident of your ability to do these things? Be specific.

…with some help. This must be addressed quickly because topics you do not master become potholes in your road to success. In math, every topic builds upon previous work. It is important to make sure you have a strong foundation before you move on. Whom can you ask for help? Your fellow classmates and instructor are good resources. Is there a place on campus where math tutors are available? Can your study skills be improved?

…no—I don’t get it! This is a warning sign and you must not ignore it. You should get help right away or you will quickly be overwhelmed. See your instructor as soon as you can to discuss your situation. Together you can come up with a plan to get you the help you need.