Lesson plan

8. Using known facts to add three addends (FP)

teaches Common Core State Standards CCSS.Math.Content.1.OA.B.3 http://corestandards.org/Math/Content/1/OA/B/3
teaches Common Core State Standards CCSS.Math.Practice.MP8 http://corestandards.org/Math/Practice/MP8
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Lesson objective: Add three addends by grouping known facts such as tens or doubles to help solve problems more efficiently.

This lesson helps to build fluency with addition of three addends. A ten frame is used here because it supports the concept of making a ten and adding a value to ten. This work develops students' understanding that when we are adding numbers, it doesn't matter how they are grouped.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they use facts they already know in order to make adding three numbers more efficient.

Key vocabulary:

  • addend: one of the numbers in an indicated sum of two or more numbers (e.g., 4 + 3 + 1 = 8; 4, 3, and 1 are addends)

  • double fact: an addition equation in which each addend is the same
  • equation: a mathematical sentence stating that two expressions are equal

  • group: a number of people or objects that are assembled together or that have some unifying relationship
  • known fact: an equation that can be automatically and correctly stated without counting
  • sum: the result when two or more quantities are added
  • ten fact: an addition equation with two addends that total or equal ten

Special materials needed:

  • double ten frames
  • multi-colored counters