1. Add Three Numbers Unit of Study: Addition and Subtraction Strategies to 20 Global Concept Guide: 5 of 5

2. Content Development  The Associative Property of Addition is a rule. a+(b+c)=(a+b)=+c  When adding more than two addends you can still only add two numbers at a time, but you can choose which two to add first.  Students do not need to learn the name of the property or memorize the definition. They need to understand how the property works and how to use it.  “Using the Associative Property provides an excellent opportunity for children to apply a variety of addition strategies. Encourage children to analyze the addends to determine which two might make sense to add first.” Go Math p.133A

3. Day 1  Use problem solving scenarios, such as the Listen and Draw on Go Math p 133, to give students the opportunities to use manipulatives to represent the objects in the problem. They should be able to show how they are grouping the addends to find the sum. Encourage students to explain why they are choosing to add those two numbers first.  Use a variety of students’ strategies to share with the class. Have a discussion about how the strategies are different but the sums are the same. Allow students to share their reasoning about why they chose to add the addends in that order.  Use students’ strategies from today to begin an anchor chart about the Associative Property of Addition.

4. Day 2  Begin the day with a problem solving scenario, such as the Listen and Draw on Go Math page 142. Prior to using their book, read the problem to the students and have them solve it in their journals. Allow them to use manipulatives if necessary. Share and compare as on Day 1.  Based on informal assessments collected on Day 1 and the beginning of Day 2 you can then differentiate as necessary.  The problems in Lesson 3.12 pages 143 and 144 would be a good idea to use today. You can assign students particular problems based on their need; however, do continue to have students verbalize or write why they are choosing the two addends that they are adding first. Check for students’ use of addition strategies.

5. 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 page 133B—enrich activity Reteach/Intervention: (small group)  Go Math page 133B—Tier 1 reteach activity, ELL Language Support, Tier 2 activity; page 137B—Tier 1 reteach activity.