Lesson objective: Solve problems using the commutative property of addition.

This lesson provides an opportunity for students to apply their knowledge and understanding of the commutative property of addition to a real-life situation. Students are asked to use the commutative property to determine whether or not there will be enough pizza for 12 kids to get a slice at a pizza party.

Key Concept students will use:

- The commutative property can be applied to addition.

Skills students will use:

- Knowing how to solve addition and subtraction word problems (K.OA.A.2)
- Using interlocking cubes to prove the commutative property of addition

Students engage in Mathematical Practice 3 (Construct viable arguments and critique the reasoning of others) as they count on using interlocking cubes or number lines to write equations that prove whether or not there will be enough pizza for each kid at the party.

**Key vocabulary: **

- addends
- addition
- commutative property of addition
- equation

**Special materials needed:**

- interlocking cubes
- number lines