Lesson objective: Apply properties of operations to add.

This lesson helps to build fluency with addition within 20. Connecting cubes are used because this model supports the development of computational strategies. This work develops students' understanding of the commutative property of addition.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they work with connecting cubes to build models of the commutative property of addition by showing that the order of the addends doesn't change the total.

**Key vocabulary:**

- addends
- addition
- equal
- equation
- sum
- total

**Special materials needed:**

- connecting cubes