 # Standard 2 : Build fractions from unit fractions by applying and extending previous understandings of operations on whole numbers. (Major Cluster) (Archived)

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Clusters should not be sorted from Major to Supporting and then taught in that order. To do so would strip the coherence of the mathematical ideas and miss the opportunity to enhance the major work of the grade with the supporting clusters.

### General Information

Number: MAFS.4.NF.2
Title: Build fractions from unit fractions by applying and extending previous understandings of operations on whole numbers. (Major Cluster)
Type: Cluster
Subject: Mathematics - Archived
Domain-Subdomain: Number and Operations - Fractions

#### Related Standards

This cluster includes the following benchmarks
Code Description
MAFS.4.NF.2.3: Understand a fraction a/b with a > 1 as a sum of fractions 1/b.
1. Understand addition and subtraction of fractions as joining and separating parts referring to the same whole.
2. Decompose a fraction into a sum of fractions with the same denominator in more than one way, recording each decomposition by an equation. Justify decompositions, e.g., by using a visual fraction model. Examples: 3/8 = 1/8 + 1/8 + 1/8 ; 3/8 = 1/8 + 2/8 ; 2 1/8 = 1 + 1 + 1/8 = 8/8 + 8/8 + 1/8.
3. Add and subtract mixed numbers with like denominators, e.g., by replacing each mixed number with an equivalent fraction, and/or by using properties of operations and the relationship between addition and subtraction.
4. Solve word problems involving addition and subtraction of fractions referring to the same whole and having like denominators, e.g., by using visual fraction models and equations to represent the problem.
 Clarifications:Examples of Opportunities for In-Depth Focus This standard represents an important step in the multi-grade progression for addition and subtraction of fractions. Students extend their prior understanding of addition and subtraction to add and subtract fractions with like denominators by thinking of adding or subtracting so many unit fractions.
MAFS.4.NF.2.4: Apply and extend previous understandings of multiplication to multiply a fraction by a whole number.
1. Understand a fraction a/b as a multiple of 1/b. For example, use a visual fraction model to represent 5/4 as the product 5 × (1/4), recording the conclusion by the equation 5/4 = 5 × (1/4).
2. Understand a multiple of a/b as a multiple of 1/b, and use this understanding to multiply a fraction by a whole number. For example, use a visual fraction model to express 3 × (2/5) as 6 × (1/5), recognizing this product as 6/5. (In general, n × (a/b) = (n × a)/b.)
3. Solve word problems involving multiplication of a fraction by a whole number, e.g., by using visual fraction models and equations to represent the problem. For example, if each person at a party will eat 3/8 of a pound of roast beef, and there will be 5 people at the party, how many pounds of roast beef will be needed? Between what two whole numbers does your answer lie?
 Clarifications:Examples of Opportunities for In-Depth Focus This standard represents an important step in the multi-grade progression for multiplication and division of fractions. Students extend their developing understanding of multiplication to multiply a fraction by a whole number.

#### Related Access Points

This cluster includes the following access points.

#### Access Points

 Access Point Number Access Point Title MAFS.4.NF.2.AP.3a: Using a representation, decompose a fraction into multiple copies of a unit fraction (e.g., 3/4 = 1/4 + 1/4+ 1/4). MAFS.4.NF.2.AP.3b: Add and subtract fractions with like denominators (2, 3, 4 or 8) using representations. MAFS.4.NF.2.AP.3c: Solve word problems involving addition and subtraction of fractions with like denominators (2, 3, 4 or 8). MAFS.4.NF.2.AP.4a: Multiply a fraction by a whole number using a visual fraction model.

#### Related Resources

Vetted resources educators can use to teach the concepts and skills in this topic.

#### Original Student Tutorials

 Name Description Buffy's Bakery Part 4- Multiplying a Fraction by a Whole: Standard Algorithm: Help Buffy multiply fractions by whole numbers using the standard algorithm in addition to visual fraction models in this bakery-themed, interactive tutorial. This is part 4 of a 4-part series. Click below to open other tutorials in the series. Buffy’s Bakery Part 3: Using Models to Multiply a Fraction by a Whole Number: Help Buffy the Baker multiply a fraction by a whole using models in this sweet interactive tutorial. This is part 3 of a 4-part series. Click below to open other tutorials in the series. Multiplying Fractions with Bake Sale Mania: Find the total amounts of repeated fraction quantities by multiplying a fraction by a whole number using visual models that represent real-world problems and cookies in this interactive tutorial. The Leftover Dessert Dilemma: Learn how to decompose a fraction into a sum of fractions with common denominators with this interactive tutorial.

#### Educational Games

 Name Description Ice Ice Maybe: An Operations Estimation Game: This fun and interactive game helps practice estimation skills, using various operations of choice, including addition, subtraction, multiplication, division, using decimals, fractions, and percents. Various levels of difficulty make this game appropriate for multiple age and ability levels. Addition/Subtraction: The addition and subtraction of whole numbers, the addition and subtraction of decimals. Multiplication/Division: The multiplication and addition of whole numbers. Percentages: Identify the percentage of a whole number. Fractions: Multiply and divide a whole number by a fraction, as well as apply properties of operations. Fraction Quiz: Test your fraction skills by answering questions on this site. This quiz asks you to simplify fractions, convert fractions to decimals and percentages, and answer algebra questions involving fractions. You can even choose difficulty level, question types, and time limit.

#### Formative Assessments

 Name Description How Much Sugar?: Students are asked to multiply a fraction by a whole number to solve a word problem and to represent the product with a visual fraction model. Training for a Race: Students are asked to multiply an improper fraction by a whole number to solve a word problem and use a visual model or equation to represent the problem. How Many One Fourths?: Students are asked to multiply a fraction by a whole number and to represent the product with a visual fraction model. Fractions and Multiples: Students use a visual fraction model to explain how many one sixths are in and record their work with an equation. Adding and Subtracting Mixed Numbers: Students are given pairs of mixed numbers to either add or subtract. Fraction Word Problems: Students are asked to solve a word problem that involves subtracting fractions with like denominators. Students then analyze a word problem involving subtraction of unlike unit quantities. Decomposing Three-Fifths: Students are asked to use a visual fraction model to decompose three-fifths in two different ways. Anna Marie and the Pizza: Students are asked to solve a word problem that involves adding fractions with like denominators. Students then analyze a word problem involving addition of unlike unit quantities.

#### Lesson Plans

 Name Description Making 22 Seventeenths in Different Ways: This task is a straightforward task related to adding fractions with the same denominator. The main purpose is to emphasize that there are many ways to decompose a fraction as a sum of fractions. Comparing two different pizzas: The focus of this task is on understanding that fractions, in an explicit context, are fractions of a specific whole. In this this problem there are three different wholes: the medium pizza, the large pizza, and the two pizzas taken together. This task is best suited for instruction. Students can practice explaining their reasoning to each other in pairs or as part of a whole group discussion. Writing a Mixed Number as an Equivalent Fraction: The purpose of this task is to help students understand and articulate the reasons for the steps in the usual algorithm for converting a mixed number into an equivalent fraction. Step two shows that the algorithm is merely a shortcut for finding a common denominator between two fractions. This concept is an important precursor to adding mixed numbers and fractions with like denominators and as such, step two should be a point of emphasis. This task is appropriate for either instruction or formative assessment. Sugar in six cans of soda: This task provides a familiar context allowing students to visualize multiplication of a fraction by a whole number. This task could form part of a very rich activity which includes studying soda can labels. Peaches: This task provides a context where it is appropriate for students to subtract fractions with a common denominator; it could be used for either assessment or instructional purposes. For this particular task, teachers should anticipate two types of solution approaches: one where students subtract the whole numbers and the fractions separately and one where students convert the mixed numbers to improper fractions and then proceed to subtract. Connor and Makayla Discuss Multiplication: The purpose of this task is to have students think about the meaning of multiplying a number by a fraction, and use this burgeoning understanding of fraction multiplication to make sense of the commutative property of multiplication in the case of fractions. Plastic Building Blocks: The purpose of this task is to have students add mixed numbers with like denominators. This task illustrates the different kinds of solution approaches students might take to such a task. Two general approaches should be anticipated: one where students calculate exactly how many buckets of blocks the boys have to determine an answer, and one where students compare the given numbers to benchmark numbers.

#### Tutorials

 Name Description Multiplying a Fraction by a Whole Number: In this Khan Academy video visual fraction models are used to represent the multiplication of a whole number times a fraction. What Fraction of Spider Eyes are Looking at Me?: This Khan Academy video uses authentic pictures to present addition of two fractions with common denominators. Figuring Out How Much of a Pizza is Left: This Khan Academy video solves two word problems using visual fraction models. Comparing Fractions: This tutorial for student audiences will assist learners with a further understanding that fractions are a way of showing part of a whole. Yet some fractions are larger than others. So this tutorial will help to refresh the understanding for the comparison of fractions. Students will be able to navigate the teaching portion of the tutorial at their own pace and test their understanding after each step of the lesson with a "Try This" section. The "Try This" section will monitor students answers and self-check by a right answer turning orange and a wrong answer dissolving. Adding Fractions: In this web-based tutorial, students learn procedures for adding fractions with like and unlike denominators. The tutorial includes visual representations of the problems using pizzas, animations of the algorithm, and links to related lessons, worksheets, and practice problems.

#### Virtual Manipulative

 Name Description Fraction Game: This virtual manipulative allows individual students to work with fraction relationships. (There is also a link to a two-player version.)

#### Student Resources

Vetted resources students can use to learn the concepts and skills in this topic.

#### Original Student Tutorials

 Title Description Buffy's Bakery Part 4- Multiplying a Fraction by a Whole: Standard Algorithm: Help Buffy multiply fractions by whole numbers using the standard algorithm in addition to visual fraction models in this bakery-themed, interactive tutorial. This is part 4 of a 4-part series. Click below to open other tutorials in the series. Buffy’s Bakery Part 3: Using Models to Multiply a Fraction by a Whole Number: Help Buffy the Baker multiply a fraction by a whole using models in this sweet interactive tutorial. This is part 3 of a 4-part series. Click below to open other tutorials in the series. Multiplying Fractions with Bake Sale Mania: Find the total amounts of repeated fraction quantities by multiplying a fraction by a whole number using visual models that represent real-world problems and cookies in this interactive tutorial. The Leftover Dessert Dilemma: Learn how to decompose a fraction into a sum of fractions with common denominators with this interactive tutorial.

#### Educational Games

 Title Description Ice Ice Maybe: An Operations Estimation Game: This fun and interactive game helps practice estimation skills, using various operations of choice, including addition, subtraction, multiplication, division, using decimals, fractions, and percents. Various levels of difficulty make this game appropriate for multiple age and ability levels. Addition/Subtraction: The addition and subtraction of whole numbers, the addition and subtraction of decimals. Multiplication/Division: The multiplication and addition of whole numbers. Percentages: Identify the percentage of a whole number. Fractions: Multiply and divide a whole number by a fraction, as well as apply properties of operations. Fraction Quiz: Test your fraction skills by answering questions on this site. This quiz asks you to simplify fractions, convert fractions to decimals and percentages, and answer algebra questions involving fractions. You can even choose difficulty level, question types, and time limit.

 Title Description Making 22 Seventeenths in Different Ways: This task is a straightforward task related to adding fractions with the same denominator. The main purpose is to emphasize that there are many ways to decompose a fraction as a sum of fractions. Comparing two different pizzas: The focus of this task is on understanding that fractions, in an explicit context, are fractions of a specific whole. In this this problem there are three different wholes: the medium pizza, the large pizza, and the two pizzas taken together. This task is best suited for instruction. Students can practice explaining their reasoning to each other in pairs or as part of a whole group discussion. Writing a Mixed Number as an Equivalent Fraction: The purpose of this task is to help students understand and articulate the reasons for the steps in the usual algorithm for converting a mixed number into an equivalent fraction. Step two shows that the algorithm is merely a shortcut for finding a common denominator between two fractions. This concept is an important precursor to adding mixed numbers and fractions with like denominators and as such, step two should be a point of emphasis. This task is appropriate for either instruction or formative assessment. Sugar in six cans of soda: This task provides a familiar context allowing students to visualize multiplication of a fraction by a whole number. This task could form part of a very rich activity which includes studying soda can labels. Peaches: This task provides a context where it is appropriate for students to subtract fractions with a common denominator; it could be used for either assessment or instructional purposes. For this particular task, teachers should anticipate two types of solution approaches: one where students subtract the whole numbers and the fractions separately and one where students convert the mixed numbers to improper fractions and then proceed to subtract. Connor and Makayla Discuss Multiplication: The purpose of this task is to have students think about the meaning of multiplying a number by a fraction, and use this burgeoning understanding of fraction multiplication to make sense of the commutative property of multiplication in the case of fractions. Plastic Building Blocks: The purpose of this task is to have students add mixed numbers with like denominators. This task illustrates the different kinds of solution approaches students might take to such a task. Two general approaches should be anticipated: one where students calculate exactly how many buckets of blocks the boys have to determine an answer, and one where students compare the given numbers to benchmark numbers.

#### Tutorials

 Title Description Multiplying a Fraction by a Whole Number: In this Khan Academy video visual fraction models are used to represent the multiplication of a whole number times a fraction. What Fraction of Spider Eyes are Looking at Me?: This Khan Academy video uses authentic pictures to present addition of two fractions with common denominators. Figuring Out How Much of a Pizza is Left: This Khan Academy video solves two word problems using visual fraction models. Comparing Fractions: This tutorial for student audiences will assist learners with a further understanding that fractions are a way of showing part of a whole. Yet some fractions are larger than others. So this tutorial will help to refresh the understanding for the comparison of fractions. Students will be able to navigate the teaching portion of the tutorial at their own pace and test their understanding after each step of the lesson with a "Try This" section. The "Try This" section will monitor students answers and self-check by a right answer turning orange and a wrong answer dissolving.

#### Virtual Manipulative

 Title Description Fraction Game: This virtual manipulative allows individual students to work with fraction relationships. (There is also a link to a two-player version.)

#### Parent Resources

Vetted resources caregivers can use to help students learn the concepts and skills in this topic.