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Lesson plan

5. Explore related addition and subtraction equations (FP)

teaches Common Core State Standards MP7 http://corestandards.org/Math/Practice/MP7
teaches Common Core State Standards MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards 1.OA.B.4 http://corestandards.org/Math/Content/1/OA/B/4
teaches Common Core State Standards 1.OA.B.3 http://corestandards.org/Math/Content/1/OA/B/3

5. Explore related addition and subtraction equations (FP)

Lesson objective: Understand that subtraction can be thought of as an unknown addend problem.

This lesson helps to build strategies with addition and subtraction. Fact family triangle diagrams and number lines are used here because they show the number partners in related addition and subtraction facts. This work develops students' understanding that subtraction can be thought of as an unknown addend problem.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they prove the inverse relationship between addition and subtraction. 

Key vocabulary:

  • inverse operation
  • unknown addend

Special materials needed:

  • number line