Learning Outcomes
- Write fractions that represent portions of objects
- Identify the numerator and the denominator of a fraction
- Use fraction circles to make wholes given
- Use models to visualize improper fractions and mixed numbers.
Representing Parts of a Whole as 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 1212 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 1414 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 112112 of the pizza.
Fractions
A fraction is written abab, where aa and bb are integers and b≠0b≠0. In a fraction, aa is called the numerator and bb is called the denominator.
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, bb, cannot equal zero because division by zero is undefined.
In the image below, the circle has been divided into three parts of equal size. Each part represents 1313 of the circle. This type of model is called a fraction circle. Other shapes, such as rectangles, can also be used to model fractions.
Doing the Manipulative Mathematics activity Model Fractions will help you develop a better understanding of fractions, their numerators and denominators.
What does the fraction 2323 represent? The fraction 2323 means two of three equal parts.
Example
Name the fraction of the shape that is shaded in each of the figures.
Solution:
We need to ask two questions. First, how many equal parts are there? This will be the denominator. Second, of these equal parts, how many are shaded? This will be the numerator.
How many equal parts are there?There are eight equal parts.How many are shaded?Five parts are shaded.How many equal parts are there?There are eight equal parts.How many are shaded?Five parts are shaded.
Five out of eight parts are shaded. Therefore, the fraction of the circle that is shaded is 5858.
How many equal parts are there?There are nine equal parts.How many are shaded?Two parts are shaded.How many equal parts are there?There are nine equal parts.How many are shaded?Two parts are shaded.
Two out of nine parts are shaded. Therefore, the fraction of the square that is shaded is 2929.
Example
Shade 3434 of the circle.
Try it
Shade 6868 of the circle.
Shade 2525 of the rectangle.
Watch the following video to see more examples of how to write fractions given a model.
In earlier examples, we used circles and rectangles to model fractions. Fractions can also be modeled as manipulatives called fraction tiles, as shown in the image below. 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 the fraction tiles above to answer the following questions:
How many 1212 tiles does it take to make one whole tile? | It takes two halves to make a whole, so two out of two is 22=122=1. |
How many 1313 tiles does it take to make one whole tile? | It takes three thirds, so three out of three is 33=133=1. |
How many 1414 tiles does it take to make one whole tile? | It takes four fourths, so four out of four is 44=144=1. |
How many 1616 tiles does it take to make one whole tile? | It takes six sixths, so six out of six is 66=166=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 124124 tiles does it take to make one whole tile? | It takes 2424 twenty-fourths, so 2424=12424=1. |
This leads us to the Property of One.
Property of One
Any number, except zero, divided by itself is one.
aa=1(a≠0)aa=1(a≠0)
Example
Use fraction circles to make wholes using the following pieces:
- 44 fourths
- 55 fifths
- 66 sixths
Try it
Use fraction circles to make wholes with the following pieces: 33 thirds.
Use fraction circles to make wholes with the following pieces: 88 eighths.
What if we have more fraction pieces than we need for 11 whole? We’ll look at this in the next example.
Example
Use fraction circles to make wholes using the following pieces:
- 33 halves
- 88 fifths
- 77 thirds
try it
Use fraction circles to make wholes with the following pieces: 55 thirds.
Use fraction circles to make wholes with the following pieces: 55 halves.
Model Improper Fractions and Mixed Numbers
In an earlier example, 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, 1515, so altogether you had eight fifths, which we can write as 8585. The fraction 8585 is one whole, 11, plus three fifths, 3535, or 135135, which is read as one and three-fifths.
The number 135135 is called a mixed number. A mixed number consists of a whole number and a fraction.
Mixed Numbers
A mixed number consists of a whole number aa and a fraction bcbc where c≠0c≠0. It is written as follows.
abc, c≠0abc, c≠0
Fractions such as 54,32,5554,32,55, and 7373 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 12,3712,37, and 11181118 are proper fractions.
Proper and Improper Fractions
The fraction abab is a proper fraction if [latex]a
Example
Name the improper fraction modeled. Then write the improper fraction as a mixed number.
try it
Example
Draw a figure to model 118.
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Draw a figure to model 76
Draw a figure to model 65
Example
Use a model to rewrite the improper fraction 116 as a mixed number.
Try it
In the next video we show another way to draw a model that represents a fraction. You will see example of both proper and improper fractions shown.
Example
Use a model to rewrite the mixed number 145 as an improper fraction.
Try it
Candela Citations
- Question ID 145976, 145977, 145974, 145981, 145982, . Authored by: Lumen Learning. License: CC BY: Attribution. License Terms: IMathAS Community License CC-BY + GPL
- Ex: Determine the Fraction Modeled. Authored by: James Sousa (Mathispower4u.com). Located at: https://youtu.be/c_yIA4OQ4qA. License: CC BY: Attribution
- Draw Models of Fractions and Explain the Meaning of the Fraction. Authored by: James Sousa (Mathispower4u.com). Located at: https://youtu.be/akyByv80Uzc. License: CC BY: Attribution
- Prealgebra. Provided by: OpenStax. License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/caa57dab-41c7-455e-bd6f-f443cda5519c@9.757