## Commutative and Associative Properties

Developing the Concept

Once students feel comfortable in recognizing the patterns in the addition table, you can formalize two important properties. Students will use these properties again in multiplication. New names for the properties will be introduced.

**Materials: **chalkboard and chalk

**Preparation: **Poster identifying the Commutative Property for Addition, using numerical examples. Poster identifying the Associative Property for Addition, using numerical examples.

**Prerequisite Skills and Concepts: **Students should know how to add and subtract 2-digit numbers, with regrouping. Students should know the addition and subtraction fact families to 20.

Write the problems 54 + 67 and 67 + 54 on the board in vertical format.

**Wrap-Up and Assessment Hints**

Students need practice with the Commutative and Associative Properties in order to realize how powerful they are for mental math. As you assess students, find out how they are thinking and select a strategy that builds on what they already know. Encourage students to use these patterns and relationships while solving word problems.