Lesson plan

4. Understand decomposing numbers to 10 (C)

teaches Common Core State Standards CCSS.Math.Content.K.OA.A.1 http://corestandards.org/Math/Content/K/OA/A/1
teaches Common Core State Standards CCSS.Math.Content.K.OA.A.2 http://corestandards.org/Math/Content/K/OA/A/2
teaches Common Core State Standards CCSS.Math.Content.K.OA.A.3 http://corestandards.org/Math/Content/K/OA/A/3
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4
teaches Common Core State Standards CCSS.Math.Practice.MP5 http://corestandards.org/Math/Practice/MP5
teaches Common Core State Standards CCSS.Math.Practice.MP6 http://corestandards.org/Math/Practice/MP6
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Lesson objective: Decompose numbers less than or equal to 10 into pairs in more than one way.

Students bring prior knowledge of addition and subtraction from K.OA.A.1. This prior knowledge is extended to decomposing numbers into pairs in more than one way as students decompose the number eight. A conceptual challenge students may encounter is not recognizing that the total stays the same. 

The concept is developed through work with groups of counters, which are taken apart as students decompose the number.

This work helps students deepen their understanding of number because students develop an understanding that numbers can be taken apart in different ways.

Students engage in Mathematical Practice 4 (Model with mathematics) as they show different ways that the number eight can be decomposed.

Key vocabulary:

  • decompose
  • subtraction
  • total

Special materials needed:

  • hoops or mats for students to act out the story problem
  • manipulatives, such as counters