Lesson plan

7. Understand the Associative Property when using 3 addends (C)

teaches Common Core State Standards CCSS.Math.Content.1.OA.A.2 http://corestandards.org/Math/Content/1/OA/A/2
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.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 we can group addends by known facts to solve problems more efficiently.

Students bring prior knowledge of making a ten from K.OA.A.4. This prior knowledge is extended to adding three numbers as students group them by known facts such as making a ten or doubles. A conceptual challenge students may encounter is thinking they must add the numbers in order or start with the larger number even though there may be a more efficient way. 

The concept is developed through work with a double ten frame, which helps build the concept of making a ten.

This work helps students deepen their understanding of equivalence because any way we group the numbers, they have the same sum.

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they determine the meaning and work towards finding a possible solutions. Students will also engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they look for ways to decompose numbers into three addends that include partners of ten. 

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)

  • addition: a mathematical operation of combining two or more numbers into a total or sum

  • decompose: to break a number into smaller units to simplify computation

  • double fact: an addition equation in which each addend is the same
  • equal: having the same amount, size, number, or value

  • equation: a mathematical sentence stating that two expressions are equal

  • sum: the result when two or more quantities are added

  • ten fact: an addition equation including two addends that total or equal ten
  • ten frame: a visual array model that has two sets of five connected squares

Special materials needed:

  • double ten frame 
  • multi-colored counters