Lesson objective: Solve problems using the commutative and associative properties with algebraic expressions.

This lesson provides an opportunity for students to apply their knowledge and understanding of the commutative and associative properties to a real-life situation. Students are asked to find the number of pencils which are contained in equal sized packs of pencils and the total number of pencils each of the three children take.

Key Concept students will use:

- The associative and commutative properties apply to algebraic expressions just as they do to numeric expressions.

Skills students will use:

- Order of operations to evaluate numeric expressions (Grade 5, Unit 13).
- The associative and commutative properties to rewrite an expression.
- Evaluate algebraic expressions at specific values of the variable.

Students engage in Mathematical Practice 7 (look for and make use of structure) as they write algebraic expressions representing the number of pencils each student has taken and the total number of pencils taken. Students will use the associative and commutative properties to rewrite an expression so that it is easier to use in solving the problem. They will examine the meaning of the value of an expression as they find the number of pencils contained in each pack of pencils.

**Key vocabulary: **

- associative
- commutative
- equivalent
- expression
- value