Prealgebra 2e · free preview

4.1 Visualize Fractions

Learning objectives: Understand the meaning of fractions; Model improper fractions and mixed numbers; Convert between improper fractions and mixed numbers; Model equivalent fractions; Find equivalent fractions; Locate fractions and mixed numbers on the number line; Order fractions and mixed numbers

1. Learning objectives

Learning objectives

Learning objectives

  • Understand the meaning of fractions
  • Model improper fractions and mixed numbers
  • Convert between improper fractions and mixed numbers
  • Model equivalent fractions
  • Find equivalent fractions
  • Locate fractions and mixed numbers on the number line
  • Order fractions and mixed numbers

2. Understand the Meaning of 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\frac{1}{2} to mean one out of two parts.

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\frac{1}{4} of the pizza.

On Wednesday, the family invites some friends over for a pizza dinner. There are a total of 1212 people. If they share the pizza equally, each person would get 112\frac{1}{12} of the pizza.

A fraction is a way to represent parts of a whole. The denominator bb represents the number of equal parts the whole has been divided into, and the numerator aa represents how many parts are included. The denominator, b,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\frac{1}{3} of the circle. This type of model is called a fraction circle. Other shapes, such as rectangles, can also be used to model fractions.

What does the fraction 23\frac{2}{3} represent? The fraction 23\frac{2}{3} means two of three equal parts.

3. Example 4.1

Example 4.1

Example 4.1

Name the fraction of the shape that is shaded in each of the figures.

Solution

  1. Identify the circle's equal parts. For part (a), the circle is divided into eight equal regions, so the denominator of the shaded fraction must be 88.
  2. Count the shaded circle regions. Five of the eight regions in part (a) are shaded, so the numerator is 55 and the fraction is 58\frac{5}{8}.
  3. Identify the square's equal parts. For part (b), the square is divided into nine equal regions, so the denominator of the shaded fraction must be 99.
  4. Count the shaded square regions. Two of the nine regions in part (b) are shaded, so the numerator is 22 and the fraction is 29\frac{2}{9}.
  5. State both shaded fractions. The circle is 58\frac{5}{8} shaded, and the square is 29\frac{2}{9} shaded, because each numerator counts shaded parts and each denominator counts all equal parts.

Takeaway: To read a fraction from a shaded figure, put the number of shaded equal parts in the numerator and the total number of equal parts in the denominator, giving 58\frac{5}{8} and 29\frac{2}{9}.

4. Example 4.2

Example 4.2

Example 4.2

Shade 34\frac{3}{4} of the circle.

Solution

  1. Use the denominator to set the partitions. The target is 34\frac{3}{4}, so the circle must be divided into four equal parts so that each part represents one-fourth of the whole.
  2. Divide the circle into equal regions. The four regions must have the same size, because a fraction model represents equal pieces and a different region size would not represent one-fourth each.
  3. Use the numerator to select regions. Since the numerator is 33, shade exactly three of the four equal regions and leave the remaining fourth region unshaded.
  4. Check the completed model. The model contains three shaded fourths out of four equal fourths, so the shaded part represents 34\frac{3}{4} of the circle.

Takeaway: To shade a fraction of a whole, divide the shape into as many equal parts as the denominator and shade the number of parts named by the numerator, so 34\frac{3}{4} uses three of four parts.

In Example 4.1 and Example 4.2, 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.

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\frac{1}{2} 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.\frac{2}{2}=1.
How many 13\frac{1}{3} tiles does it take to make one whole tile?It takes three thirds, so three out of three is 33=1.\frac{3}{3}=1.
How many 14\frac{1}{4} tiles does it take to make one whole tile?It takes four fourths, so four out of four is 44=1.\frac{4}{4}=1.
How many 16\frac{1}{6} tiles does it take to make one whole tile?It takes six sixths, so six out of six is 66=1.\frac{6}{6}=1.
What if the whole were divided into 2424 equal parts? (We have not shown fraction tiles to represent this, but try to visualize it in your mind.) How many 124\frac{1}{24} tiles does it take to make one whole tile?It takes 2424 twenty-fourths, so 2424=1.\frac{24}{24}=1.

It takes 2424 twenty-fourths, so 2424=1.\frac{24}{24}=1.

This leads us to the Property of One.

Any number, except zero, divided by itself is one.

aa=1 (a≠0)\frac{a}{a}=1\,(a\ne{}0)

5. Example 4.3

Example 4.3

Example 4.3

Use fraction circles to make wholes using the following pieces:

  1. ⓐ 44 fourths
  2. ⓑ 55 fifths
  3. ⓒ 66 sixths

Solution

  1. Identify the size of each piece. The pieces are fourths, fifths, and sixths, so one whole contains 44 fourths, 55 fifths, or 66 sixths.
  2. Build each whole. ⓐ Use 44 fourths to fill one circle. ⓑ Use 55 fifths to fill one circle. ⓒ Use 66 sixths to fill one circle.
  3. State the wholes made. The pieces make 11 whole in ⓐ, 11 whole in ⓑ, and 11 whole in ⓒ, with no pieces left over.

Takeaway: A fraction circle makes exactly one whole when it contains as many equal pieces as the denominator of the unit fraction.

What if we have more fraction pieces than we need for 11 whole? We’ll look at this in the next example.

6. Example 4.4

Example 4.4

Example 4.4

Use fraction circles to make wholes using the following pieces:

  1. ⓐ 33 halves
  2. ⓑ 88 fifths
  3. ⓒ 77 thirds

Solution

  1. Group the three halves. A whole requires two halves, and 3=1⋅2+13=1\cdot 2+1, so the pieces make 11 whole with 11 half left over.
  2. Group the eight fifths. A whole requires five fifths, and 8=1⋅5+38=1\cdot 5+3, so the pieces make 11 whole with 33 fifths left over.
  3. Group the seven thirds. A whole requires three thirds, and 7=2⋅3+17=2\cdot 3+1, so the pieces make 22 wholes with 11 third left over.
  4. Match each remainder to its size. The leftover pieces in the three groups are respectively 11 half, 33 fifths, and 11 third because each remainder uses the denominator of that group.
  5. State the three mixed numbers. Therefore the groups represent 1121\frac{1}{2}, 1351\frac{3}{5}, and 2132\frac{1}{3}, respectively.

Takeaway: To combine fractional pieces into wholes, divide the number of pieces by the denominator and retain the remainder, giving 1121\frac{1}{2}, 1351\frac{3}{5}, and 2132\frac{1}{3}.

7. Model Improper Fractions and Mixed Numbers

Model Improper Fractions and Mixed Numbers

In Example 4.4 (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,\frac{1}{5}, so altogether you had eight fifths, which we can write as 85.\frac{8}{5}. The fraction 85\frac{8}{5} is one whole, 1,1, plus three fifths, 35,\frac{3}{5}, or 135,1\frac{3}{5}, which is read as one and three-fifths.

The number 1351\frac{3}{5} is called a mixed number. A mixed number consists of a whole number and a fraction.

Definition · Mixed Numbers

A mixed number consists of a whole number aa and a fraction bc\frac{b}{c} where c≠0.c\ne{}0. It is written as follows.

abc c≠0a\frac{b}{c}\,c\ne{}0

Fractions such as 54,32,55,\frac{5}{4},\frac{3}{2},\frac{5}{5}, and 73\frac{7}{3} 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,\frac{1}{2},\frac{3}{7}, and 1118\frac{11}{18} are proper fractions.

Definition · Proper and Improper Fractions

The fraction ab\frac{a}{b} is a proper fraction if a<ba<b and an improper fraction if a≥b.a\ge{}b.

8. Example 4.5

Example 4.5

Example 4.5

Name the improper fraction modeled. Then write the improper fraction as a mixed number.

Solution

  1. Identify the size of each shaded piece. Every circle is divided into three equal pieces, and each piece represents one-third of one whole circle.
  2. Count all four shaded pieces. The model contains four shaded thirds, so its improper fraction has numerator 44 and denominator 33, giving 43\frac{4}{3}.
  3. Separate the complete group. Three of the shaded pieces fill one whole circle, leaving one additional third outside that complete group.
  4. Write the mixed number. The complete group contributes 11 whole and the remaining piece contributes 13\frac{1}{3}, so 43=113\frac{4}{3}=1\frac{1}{3}.

Takeaway: An improper fraction whose numerator is the denominator plus a remainder can be rewritten by dividing to obtain the whole-number part and keeping the remainder over the original denominator, so 43=113\frac{4}{3}=1\frac{1}{3}.

9. Example 4.6

Example 4.6

Example 4.6

Draw a figure to model 118.\frac{11}{8}.

Solution

  1. Determine the unit-piece size. The denominator 88 tells us that each circle should be divided into eight equal parts, making every part one-eighth of a whole circle.
  2. Model the first complete group. Shade all eight parts of the first circle to represent 88 eighths, which is exactly 11 whole because 88=1\frac{8}{8}=1.
  3. Model the remaining pieces. The fraction 118\frac{11}{8} has three more eighths than the first group because 11−8=311-8=3, so shade three parts of a second circle.
  4. Combine the two groups. The complete circle gives 11 whole and the partial circle gives 38\frac{3}{8}, so the model represents 118=138\frac{11}{8}=1\frac{3}{8}.

Takeaway: To model an improper fraction, fill one whole with denominator-many pieces and use a second figure for the remaining numerator-minus-denominator pieces, so 118=138\frac{11}{8}=1\frac{3}{8}.

10. Example 4.7

Example 4.7

Example 4.7

Use a model to rewrite the improper fraction 116\frac{11}{6} as a mixed number.

Solution

  1. Interpret the numerator as unit pieces. The improper fraction 116\frac{11}{6} represents eleven sixths, so begin with a model containing eleven equal pieces of size one-sixth.
  2. Remove one complete group. Six sixths make exactly one whole because 66=1\frac{6}{6}=1, so remove six pieces from the original group.
  3. Identify the leftover pieces. After removing six pieces, 11−6=511-6=5 pieces remain, and those five pieces represent the fraction 56\frac{5}{6}.
  4. Combine the whole and remainder. The original group therefore contains one whole and five sixths, giving 116=156\frac{11}{6}=1\frac{5}{6}.

Takeaway: Converting 116\frac{11}{6} to a mixed number means removing one whole of six sixths and keeping the remaining five sixths, so 116=156\frac{11}{6}=1\frac{5}{6}.

11. Example 4.8

Example 4.8

Example 4.8

Use a model to rewrite the mixed number 1451\frac{4}{5} as an improper fraction.

Solution

  1. Rewrite the whole as unit pieces. The mixed number 1451\frac{4}{5} means one whole plus four fifths, and one whole equals 55\frac{5}{5}.
  2. Add like-sized pieces. The two parts together are 55+45=95\frac{5}{5}+\frac{4}{5}=\frac{9}{5}.
  3. State the improper fraction. Therefore 145=95.1\frac{4}{5}=\frac{9}{5}.

Takeaway: To convert a mixed number to an improper fraction, use the original denominator and add the fractional numerator to the whole times that denominator.

12. Convert between Improper Fractions and Mixed Numbers

Convert between Improper Fractions and Mixed Numbers

In Example 4.7, we converted the improper fraction 116\frac{11}{6} to the mixed number 1561\frac{5}{6} using fraction circles. We did this by grouping six sixths together to make a whole; then we looked to see how many of the 1111 pieces were left. We saw that 116\frac{11}{6} made one whole group of six sixths plus five more sixths, showing that 116=156.\frac{11}{6}=1\frac{5}{6}.

The division expression 116\frac{11}{6} (which can also be written as 611611) tells us to find how many groups of 66 are in 11.11. To convert an improper fraction to a mixed number without fraction circles, we divide.

13. Example 4.9

Example 4.9

Example 4.9

Convert 116\frac{11}{6} to a mixed number.

Solution

  1. Divide the numerator by the denominator. Set up 11÷611\div 6; the figure labels 66 as the divisor because the denominator determines the size of each fractional part.
  2. Read the quotient and remainder. Since 6⋅1=66\cdot 1=6 and 11−6=511-6=5, the quotient is 11 and the remainder is 55, with 5<65<6.
  3. Write the mixed number. The quotient 11 gives the whole-number part, and the remainder 55 goes over the original divisor 66, so 116=156\frac{11}{6}=1\frac{5}{6}.

Takeaway: In mixed-number division, the quotient gives the wholes and the remainder must be written over the original denominator.

Convert an improper fraction to a mixed number.

  1. Step 1. Divide the denominator into the numerator.
  2. Step 2. Identify the quotient, remainder, and divisor.
  3. Step 3. Write the mixed number as quotient remainderdivisor\frac{\mathrm{remainder}}{\mathrm{divisor}}.

14. Example 4.10

Example 4.10

Example 4.10

Convert the improper fraction 338\frac{33}{8} to a mixed number.

Solution

  1. Divide the numerator by the denominator. Set up 33÷833\div 8, as represented by the long-division figure.
  2. Find the whole part. Because 8⋅4=328\cdot 4=32, the quotient is 44 and 33−32=133-32=1 is the remainder.
  3. Write the mixed number. Use the remainder over the divisor, giving 338=418.\frac{33}{8}=4\frac{1}{8}.

Takeaway: A remainder smaller than the divisor is already reduced, so it becomes the numerator of the fractional part directly.

In Example 4.8, we changed 1451\frac{4}{5} 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\frac{5}{5}+\frac{4}{5}=\frac{9}{5}

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.

15. Example 4.11

Example 4.11

Example 4.11

Convert the mixed number 4234\frac{2}{3} to an improper fraction.

Solution

  1. Replace the whole with third-sized pieces. Multiply the whole number by the denominator: 4⋅3=124\cdot 3=12.
  2. Add the fractional pieces. The remaining 22 thirds give 12+2=1412+2=14 thirds, so the improper fraction is 143\frac{14}{3}.
  3. Interpret the sequence of figures. The four diagrams show the product 4⋅34\cdot 3, then 12+212+2 in the numerator, and finally 1414 over 33. Thus 423=143.4\frac{2}{3}=\frac{14}{3}.

Takeaway: Converting a mixed number to an improper fraction means multiplying by the denominator, adding the numerator, and keeping the denominator unchanged.

Convert a mixed number to an improper fraction.

  1. Step 1. Multiply the whole number by the denominator.
  2. Step 2. Add the numerator to the product found in Step 1.
  3. Step 3. Write the final sum over the original denominator.

16. Example 4.12

Example 4.12

Example 4.12

Convert the mixed number 102710\frac{2}{7} to an improper fraction.

Solution

  1. Replace the whole with seventh-sized pieces. Multiply the whole number by the denominator: 10⋅7=7010\cdot 7=70.
  2. Add the fractional pieces. The remaining 22 sevenths give 70+2=7270+2=72 sevenths.
  3. Interpret the sequence of figures. The diagrams show 10⋅710\cdot 7, then 70+270+2, and finally 7272 over 77. Therefore 1027=727.10\frac{2}{7}=\frac{72}{7}.

Takeaway: The numerator of an improper fraction representing a mixed number is the whole multiplied by the denominator plus the fractional numerator.

17. Model Equivalent Fractions

Model Equivalent Fractions

Let’s think about Andy and Bobby and their favorite food again. If Andy eats 12\frac{1}{2} of a pizza and Bobby eats 24\frac{2}{4} of the pizza, have they eaten the same amount of pizza? In other words, does 12=24?\frac{1}{2}=\frac{2}{4}? We can use fraction tiles to find out whether Andy and Bobby have eaten equivalent parts of the pizza.

Definition · Equivalent Fractions

Equivalent fractions are fractions that have the same value.

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\frac{1}{2} tile. How many fourths equal one-half? How many of the 14\frac{1}{4} tiles exactly cover the 12\frac{1}{2} tile?

Since two 14\frac{1}{4} tiles cover the 12\frac{1}{2} tile, we see that 24\frac{2}{4} is the same as 12,\frac{1}{2}, or 24=12.\frac{2}{4}=\frac{1}{2}.

How many of the 16\frac{1}{6} tiles cover the 12\frac{1}{2} tile?

Since three 16\frac{1}{6} tiles cover the 12\frac{1}{2} tile, we see that 36\frac{3}{6} is the same as 12.\frac{1}{2}.

So, 36=12.\frac{3}{6}=\frac{1}{2}. The fractions are equivalent fractions.

Doing the activity "Equivalent Fractions" will help you develop a better understanding of what it means when two fractions are equivalent.

18. Example 4.13

Example 4.13

Example 4.13

Use fraction tiles to find equivalent fractions. Show your result with a figure.

  1. ⓐ How many eighths equal one-half?
  2. ⓑ How many tenths equal one-half?
  3. ⓒ How many twelfths equal one-half?

Solution

  1. Match the eighth-sized tiles. Four tiles of size one-eighth cover a one-half tile exactly, so 44 eighths equal one-half and 48=12\frac{4}{8}=\frac{1}{2}.
  2. Match the tenth-sized tiles. Five tiles of size one-tenth cover a one-half tile exactly, so 55 tenths equal one-half and 510=12\frac{5}{10}=\frac{1}{2}.
  3. Match the twelfth-sized tiles. Six tiles of size one-twelfth cover a one-half tile exactly, so 66 twelfths equal one-half and 612=12\frac{6}{12}=\frac{1}{2}.
  4. Count the twentieth-sized tiles. Ten tiles of size one-twentieth cover a one-half tile exactly, because ten twentieths equal one whole, so 1020=12\frac{10}{20}=\frac{1}{2}.
  5. Confirm the equal values. The fractions 24\frac{2}{4}, 36\frac{3}{6}, 48\frac{4}{8}, 510\frac{5}{10}, 612\frac{6}{12}, and 1020\frac{10}{20} all represent the same quantity as 12\frac{1}{2}.
  6. State the equivalent fractions. Each larger fraction has both numerator and denominator multiplied by the same nonzero factor, so all of the displayed fractions are equivalent.

Takeaway: Equivalent fractions use different-sized tiles but represent the same amount, as shown by 48=510=612=1020=12\frac{4}{8}=\frac{5}{10}=\frac{6}{12}=\frac{10}{20}=\frac{1}{2}.

19. Find Equivalent Fractions

Find Equivalent Fractions

We used fraction tiles to show that there are many fractions equivalent to 12.\frac{1}{2}. For example, 24,36,\frac{2}{4},\frac{3}{6}, and 48\frac{4}{8} are all equivalent to 12.\frac{1}{2}. When we lined up the fraction tiles, it took four of the 18\frac{1}{8} tiles to make the same length as a 12\frac{1}{2} tile. This showed that 48=12.\frac{4}{8}=\frac{1}{2}. See Example 4.13.

We can show this with pizzas, too. Figure 4.4(a) shows a single pizza, cut into two equal pieces with 12\frac{1}{2} shaded. Figure 4.4(b) shows a second pizza of the same size, cut into eight pieces with 48\frac{4}{8} shaded.

This is another way to show that 12\frac{1}{2} is equivalent to 48.\frac{4}{8}.

How can we use mathematics to change 12\frac{1}{2} into 48?\frac{4}{8}? 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:

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.

If a,b,a,b, and cc are numbers where b≠0b\ne{}0 and c≠0,c\ne{}0, then

ab=a⋅cb⋅c\frac{a}{b}=\frac{a\cdot{}c}{b\cdot{}c}

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.

So, we say that 12,24,36,\frac{1}{2},\frac{2}{4},\frac{3}{6}, and 1020\frac{10}{20} are equivalent fractions.

20. Example 4.14

Example 4.14

Example 4.14

Find three fractions equivalent to 25.\frac{2}{5}.

Solution

  1. Multiply by a factor of two. Multiplying the numerator and denominator by 22 gives 2⋅2=42\cdot 2=4 and 5⋅2=105\cdot 2=10, so one equivalent fraction is 410\frac{4}{10}.
  2. Multiply by a factor of three. Multiplying both parts by 33 gives 2⋅3=62\cdot 3=6 and 5⋅3=155\cdot 3=15, so another equivalent fraction is 615\frac{6}{15}.
  3. Multiply by a factor of five. Multiplying both parts by 55 gives 2⋅5=102\cdot 5=10 and 5⋅5=255\cdot 5=25, so a third equivalent fraction is 1025\frac{10}{25}.
  4. Check that the factors agree. Each new numerator is 22 times the chosen factor and each new denominator is 55 times that same factor.
  5. State the equivalent fractions. Therefore 410\frac{4}{10}, 615\frac{6}{15}, and 1025\frac{10}{25} are all equivalent to the original fraction 25\frac{2}{5}.

Takeaway: Multiplying both the numerator and denominator of 25\frac{2}{5} by the same nonzero factor preserves its value and produces equivalent fractions such as 410\frac{4}{10}, 615\frac{6}{15}, and 1025\frac{10}{25}.

21. Example 4.15

Example 4.15

Example 4.15

Find a fraction with a denominator of 2121 that is equivalent to 27.\frac{2}{7}.

Solution

  1. Compare the requested denominator. The original fraction is 27\frac{2}{7}, and the new denominator must be 2121, so the original denominator must be multiplied to reach 2121.
  2. Find the common multiplier. Since 7⋅3=217\cdot 3=21, the required factor is 33, and this factor is nonzero so the fraction's value is preserved.
  3. Multiply the numerator by the same factor. Applying the factor 33 to the numerator gives 2⋅3=62\cdot 3=6, which keeps the numerator and denominator in the same proportion.
  4. Keep the target denominator. The equivalent fraction therefore has numerator 66 and denominator 2121, giving 621\frac{6}{21}.
  5. Verify the equivalence. Since both parts of 27\frac{2}{7} were multiplied by 33, the fraction 621\frac{6}{21} represents the same value as the original fraction.

Takeaway: To build an equivalent fraction with denominator 2121, multiply the denominator 77 by 33 and multiply the numerator by 33 as well, giving 621\frac{6}{21}.

22. Locate Fractions and Mixed Numbers on the Number Line

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,\frac{1}{5},\frac{4}{5},3,3\frac{1}{3},\frac{7}{4},\frac{9}{2},5, and 83\frac{8}{3} on the number line.

We will start with the whole numbers 33 and 55 because they are the easiest to plot.

The proper fractions listed are 15\frac{1}{5} and 45.\frac{4}{5}. We know proper fractions have values less than one, so 15\frac{1}{5} and 45\frac{4}{5} are located between the whole numbers 00 and 1.1. The denominators are both 5,5, so we need to divide the segment of the number line between 00 and 11 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,\frac{1}{5},\frac{2}{5},\frac{3}{5}, and 45.\frac{4}{5}.

Now plot points at 15\frac{1}{5} and 45.\frac{4}{5}.

The only mixed number to plot is 313.3\frac{1}{3}. Between what two whole numbers is 313?3\frac{1}{3}? Remember that a mixed number is a whole number plus a proper fraction, so 313>3.3\frac{1}{3}>3. Since it is greater than 3,3, but not a whole unit greater, 3133\frac{1}{3} is between 33 and 4.4. We need to divide the portion of the number line between 33 and 44 into three equal pieces (thirds) and plot 3133\frac{1}{3} at the first mark.

Finally, look at the improper fractions 74,92,\frac{7}{4},\frac{9}{2}, and 83.\frac{8}{3}. Locating these points will be easier if you change each of them to a mixed number.

74=134, 92=412, 83=223\frac{7}{4}=1\frac{3}{4},\,\frac{9}{2}=4\frac{1}{2},\,\frac{8}{3}=2\frac{2}{3}

Here is the number line with all the points plotted.

23. Example 4.16

Example 4.16

Example 4.16

Locate and label the following on a number line: 34,43,53,415,\frac{3}{4},\frac{4}{3},\frac{5}{3},4\frac{1}{5}, and 72.\frac{7}{2}.

Solution

  1. Set up equal unit intervals. Mark the consecutive integers on the number line and divide each relevant interval into the number of equal parts named by the denominator.
  2. Locate the proper fraction. The value 34\frac{3}{4} lies between 00 and 11, so divide that interval into fourths and place the label three fourths of the way from 00.
  3. Convert and locate four thirds. Since 43=113\frac{4}{3}=1\frac{1}{3}, the point lies between 11 and 22, one-third of the way to the right of 11.
  4. Convert and locate five thirds. Since 53=123\frac{5}{3}=1\frac{2}{3}, the point lies between 11 and 22, two-thirds of the way to the right of 11.
  5. Locate the mixed number. The value 4154\frac{1}{5} lies between 44 and 55, one-fifth of the way to the right of 44 after that interval is divided into fifths.
  6. Convert and locate seven halves. Since 72=312\frac{7}{2}=3\frac{1}{2}, the point lies halfway between 33 and 44, which completes all five labels.

Takeaway: To plot fractions and mixed numbers on a number line, identify the interval between consecutive integers, divide that interval into denominator-many equal parts, and mark the numerator's fractional part.

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 77 is −7-7 and the opposite of −7-7 is 7.7.

Fractions have opposites, too. The opposite of 34\frac{3}{4} is −34.-\frac{3}{4}. It is the same distance from 00 on the number line, but on the opposite side of 0.0.

Thinking of negative fractions as the opposite of positive fractions will help us locate them on the number line. To locate −158-\frac{15}{8} on the number line, first think of where 158\frac{15}{8} is located. It is an improper fraction, so we first convert it to the mixed number 1781\frac{7}{8} and see that it will be between 11 and 22 on the number line. So its opposite, −158,-\frac{15}{8}, will be between −1-1 and −2-2 on the number line.

24. Example 4.17

Example 4.17

Example 4.17

Locate and label the following on the number line: 14,−14,113,−113,52,\frac{1}{4},-\frac{1}{4},1\frac{1}{3},-1\frac{1}{3},\frac{5}{2}, and −52.-\frac{5}{2}.

Solution

  1. Prepare mirrored unit intervals. Mark the integers and, for each unit interval, divide it into the number of equal parts required by the fractional part of the value being located.
  2. Locate the quarter pair. The value 14\frac{1}{4} is one-fourth of the way from 00 to 11, and −14-\frac{1}{4} is one-fourth of the way from 00 to −1-1 on the opposite side.
  3. Locate the one-third pair. The value 1131\frac{1}{3} is one-third of the way from 11 to 22, and −113-1\frac{1}{3} is one-third of the way from −1-1 to −2-2.
  4. Locate the half pair. The value 52=212\frac{5}{2}=2\frac{1}{2} is halfway from 22 to 33, and −52=−212-\frac{5}{2}=-2\frac{1}{2} is halfway from −2-2 to −3-3.
  5. Check the opposite locations. Each negative label is the mirror image of its positive counterpart across 00 and is the same distance from 00 on the opposite side.

Takeaway: Opposite numbers lie the same distance from 00 on opposite sides of the number line, so −14-\frac{1}{4} mirrors 14\frac{1}{4} and −212-2\frac{1}{2} mirrors 2122\frac{1}{2}.

25. Order Fractions and Mixed Numbers

Order Fractions and Mixed Numbers

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

26. Example 4.18

Example 4.18

Example 4.18

Order each of the following pairs of numbers, using << or >:\mathrm{>:}

  1. ⓐ −23‾−1-\frac{2}{3}\underline{\hspace{2em}}-1
  2. ⓑ −312‾−3-3\frac{1}{2}\underline{\hspace{2em}}-3
  3. ⓒ −37‾−38-\frac{3}{7}\underline{\hspace{2em}}-\frac{3}{8}
  4. ⓓ −2‾−169-2\underline{\hspace{2em}}\frac{-16}{9}

Solution

  1. Compare the first pair. Since −23-\frac{2}{3} lies between −1-1 and 00, it is greater than −1-1.
  2. Compare the second pair. The mixed number −312-3\frac{1}{2} lies one-half unit to the left of −3-3, so it is less than −3-3.
  3. Compare the third pair. Both fractions are negative, and 37<38\frac{3}{7}<\frac{3}{8}, so −37<−38-\frac{3}{7}<-\frac{3}{8}.
  4. Compare the final pair. The negative fraction −169-\frac{16}{9} lies between −2-2 and −1-1, so −2<−169-2<-\frac{16}{9}.
  5. State all orders. The results are −23>−1-\frac{2}{3}>-1, −312<−3-3\frac{1}{2}<-3, −37<−38-\frac{3}{7}<-\frac{3}{8}, and −2<−169.-2<-\frac{16}{9}.

Takeaway: Negating an inequality reverses its direction, which is why the fraction with the smaller magnitude is larger when both numbers are negative.

27. Section 4.1 Exercises

Section 4.1 Exercises

Section 4.1 Exercises

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

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

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

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

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

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

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

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

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

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

In the following exercises, order each of the following pairs of numbers, using << or >.\mathrm{>.}

Everyday Math

Writing Exercises

28. Self Check

Self Check

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

ⓑ 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.

29. Practice 1

  1. Name the fraction of the shape that is shaded in each figure:
  1. Name the fraction of the shape that is shaded in each figure:
  1. Name the improper fraction. Then write it as a mixed number.

30. Practice 3

  1. Use a model to rewrite the mixed number as an improper fraction: 138.1\frac{3}{8}.
  1. Use a model to rewrite the mixed number as an improper fraction: 156.1\frac{5}{6}.
  1. Convert the improper fraction to a mixed number: 137.\frac{13}{7}.

31. Practice 4

  1. Convert the improper fraction to a mixed number: 149.\frac{14}{9}.
  1. Convert the improper fraction to a mixed number: 237.\frac{23}{7}.
  1. Convert the improper fraction to a mixed number: 4811.\frac{48}{11}.

32. Practice 5

  1. Convert the mixed number to an improper fraction: 357.3\frac{5}{7}.
  1. Convert the mixed number to an improper fraction: 278.2\frac{7}{8}.
  1. Convert the mixed number to an improper fraction: 4611.4\frac{6}{11}.

33. Practice 6

  1. Convert the mixed number to an improper fraction: 1113.11\frac{1}{3}.
  1. Find three fractions equivalent to 35.\frac{3}{5}.
  1. Find three fractions equivalent to 45.\frac{4}{5}.

34. Practice 7

  1. Find a fraction with a denominator of 2121 that is equivalent to 67.\frac{6}{7}.
  1. Find a fraction with a denominator of 100100 that is equivalent to 310.\frac{3}{10}.
  1. Order each of the following pairs of numbers, using << or >:\mathrm{>:}
  1. ⓐ −13 __−1-\frac{1}{3}\underset{\mathrm{\_\_}}{\,}-1
  1. ⓑ −112 __−2-1\frac{1}{2}\underset{\mathrm{\_\_}}{\,}-2
  1. ⓒ −23 __−13-\frac{2}{3}\underset{\mathrm{\_\_}}{\,}-\frac{1}{3}
  1. ⓓ −3 __−73-3\underset{\mathrm{\_\_}}{\,}-\frac{7}{3}

35. Practice 8

  1. Order each of the following pairs of numbers, using << or >:\mathrm{>:}
  1. ⓐ −3__−175-3\mathrm{\_\_}-\frac{17}{5}
  1. ⓑ −214__−2-2\frac{1}{4}\mathrm{\_\_}-2
  1. ⓒ −35 __−45-\frac{3}{5}\underset{\mathrm{\_\_}}{\,}-\frac{4}{5}
  1. ⓓ −4 __−103-4\underset{\mathrm{\_\_}}{\,}-\frac{10}{3}
  1. 53\frac{5}{3}
  1. 135\frac{13}{5}

36. Practice 9

  1. 289\frac{28}{9}
  1. 4715\frac{47}{15}
  1. 1251\frac{2}{5}

37. Practice 10

  1. 2562\frac{5}{6}
  1. 2572\frac{5}{7}
  1. 3593\frac{5}{9}

38. Practice 11

  1. 13\frac{1}{3}
  1. 56\frac{5}{6}
  1. 59\frac{5}{9}

39. Practice 12

  1. −1 __−13-1\underset{\mathrm{\_\_}}{\,}-\frac{1}{3}
  1. −134 __−2-1\frac{3}{4}\underset{\mathrm{\_\_}}{\,}-2
  1. −910 __−310-\frac{9}{10}\underset{\mathrm{\_\_}}{\,}-\frac{3}{10}

40. Practice 2

  1. Name the improper fraction. Then write it as a mixed number.
  1. Use a model to rewrite the improper fraction as a mixed number: 97.\frac{9}{7}.
  1. Use a model to rewrite the improper fraction as a mixed number: 74.\frac{7}{4}.

41. Practice 13

  1. −4 __−236-4\underset{\mathrm{\_\_}}{\,}-\frac{23}{6}
  1. Music Measures Fractions are used often in music. In 44\frac{4}{4} time, there are four quarter notes in one measure.
  1. ⓐ How many measures would eight quarter notes make?
  1. ⓑ The song “Happy Birthday to You” has 2525 quarter notes. How many measures are there in “Happy Birthday to You?”
  1. Give an example from your life experience (outside of school) where it was important to understand fractions.

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