Add Three Numbers Unit of Study: Addition and Subtraction Strategies to 20 Global Concept Guide: 3 of 3

Content Development  The Associative Property of Addition states that when you add three or more numbers, you can group the numbers in any order without changing the sum. Students do not need to learn the name of the property or memorize the definition. They do need to understand how the property works and how to use it.  When adding more than two addends you can choose which two should be added first by analyzing the relationships between the addends.  Encourage students to connect to previously learned strategies like doubles or make a ten. For more detailed information Go Math Teacher Edition, About the Math, p. 133A and 137A.

Day 1 Essential Question: How can you solve an addition problem with three addends?  Use problem solving scenarios, such as the Listen and Draw on Go Math Lesson 3.10, p Provide students with opportunities to use different color snap cubes to model the different addends in the problem. They should be able to show how they are grouping the addends to find the sum. Be sure to focus on the property—I can group the addends in any order and the sum will be unchanged.  Share and Show p. 134 and On Your Own p. 135 offer opportunities for students to analyze the ways to group addends and observe that the sum does not change as a result. By the end of Day 1, students should be able to group addends, to add, in any order.

Day 2 Essential Question: How can you group numbers to add three addends?  Read aloud the scenario from the Listen and Draw problem from Go Math Lesson 3.11, p. 137 but with the student books closed. We want the children to use snap cubes to model the problem and discuss different ways to group the numbers. There are 3 children at one table. There are 6 children at another table. There are 3 children in line. How many children are there?  Using the Share and Show, p. 138, encourage students to make snap cube trains to show efficient ways to combine addends to add. For example, = 16 is more efficient than because and 8 and 2 make 10. Explicit discussion and charting of combinations will be helpful.  On Your Own, p. 139 could be a good informal checkpoint. Interview students as the complete the page on their own. Are they applying the strategies efficiently? By the end of Day 2, students will group addends to make it easier to add three addends and explain their reasoning for the grouping.

Day 3 Essential Question: What strategies can I use to solve an addition problem with three addends?  Engage: Go Math Lesson 3.12, p. 142 Try Another Problem. This problem will allow students the opportunity to draw pictures and discuss the way they would group addends to find the sum.  Partner: p. 143, Share and Show. Partner students to complete problems #2-5; differentiating as needed.  What did you draw for your picture?  How did your picture help you find the answer?  Independent: On Your Own page 144. Assign students to solve problems based on their understanding of problems on Share and Show. By the end of Day 3, students will group addends to make it easier to add three addends and explain their reasoning for the grouping.

Enrich/Reteach/Intervention Enrich:  Associative Property of Addition Class Book: Students can be given a card with three numbers on it. The students will create a story to go with their numbers. The students will then choose which two addends to add first, explain why they chose them, and then solve the problem.  Go Math p. 133B Enrich activity Reteach/Intervention:  Go Math p. 133B Tier 1 Reteach Activity, ELL Language Support, Tier 2 Activity  Go Math p. 137B Tier 1 Reteach Activity.

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