Lesson plan

5. Understand subtraction strategies (C)

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.5 http://corestandards.org/Math/Content/K/OA/A/5
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP8 http://corestandards.org/Math/Practice/MP8
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Lesson objective: Understand that using different strategies to subtract will result in the same difference.

Students bring prior knowledge of subtraction strategies from understanding addition as putting together and adding to and understanding subtraction as taking apart and taking from (Grade K, Unit 10 K; K.OA.A.1). This prior knowledge is extended to using subtraction strategies to solve real-world story problems as students work to make different combinations of 10 to model subtraction. A conceptual challenge students may encounter is that subtraction is only taking away. 

The concept is developed through work with number bonds and snap cubes, which help students understand that subtraction can be represented as take from or take apart.

This work helps students deepen their understanding of operations because it shows the student that different strategies can lead to the same difference in subtraction.

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they use strategies as entry points to problems and use them to show their thinking.  

Key vocabulary:

  • number bonds
  • number partners
  • take away strategy

Special materials needed:

  • manipulatives such as cubes, beans, etc.