# 4. Reasoning about fractions in a real-world scenario (A)

teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3b http://corestandards.org/Math/Content/4/NF/B/3/b
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4

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Lesson Objective: Solve a real-world problem by reasoning about fractions.

Application Lesson: This lesson provides an opportunity for students to apply their knowledge and understanding that non-unit fractions are composed of unit fractions to reason about fractions in a real-life situation. Students are asked to correct a recipe that uses the wrong fraction of ingredients by reasoning up and down. Skills students will use include:

-decomposition of non-unit fractions into unit fractions to identify the size of the unit fraction.

-composing unit fractions and non-unit fractions to construct one whole.

-composing unit fractions to construct any fraction with the same denominator.

Students engage in Mathematical Practice 4 (Model with mathematics) by using a description to create a model of a real-world situation, and then using that model to reason up and down with fractions. The number line is especially important in this lesson as students use it to show the distance between the obstacles. Students also make some use of Mathematical Practice 3 (Look for and express regularity in repeated reasoning) as they use unit fractions to correct Leila’s recipe.

Key vocabulary:

• unit fraction

• non-unit fraction

• decompose

Special materials needed:

• none

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