Lesson plan

Add fractions with like denominators

teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3a http://corestandards.org/Math/Content/4/NF/B/3/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.MP2 http://corestandards.org/Math/Practice/MP2
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4
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Lesson objective: Add fractions with like denominators using number lines and area models.

This lesson helps to build procedural skill with fraction addition. The number line is used here because it supports the understanding of fractions as numbers, but area models are also used in order to make clear that the properties of fractions persist regardless of the representation being used. This work develops students' understanding that the meaning of addition does not change when numbers involved are fractions.

Students engage in Mathematical Practice 4 (Model with mathematics) by modeling addition as lengths on a number line. This is especially important in the practice section of the lesson as students verify sums using the understanding that the size of the unit lengths does not change when adding fractions with like denominators. Mathematical Practice 2 (Reason abstractly and quantitatively) is important as students reason about fractions with and without the support of a number line.

Key vocabulary:

  • equal
  • number line

Special materials needed:

  • various fraction manipulatives (optional)