Lesson objective: Find missing parts to create two equivalent expressions

This lesson helps to build procedural skill with finding missing parts in order to make an equivalent expressions. Balance scales are used here because they support student understanding of balance and equality. This work develops students' understanding that the equal sign indicates balance and means that the expressions on either side have the same value.

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively)** **as they use the balance scales to create equivalent expressions.

**Key vocabulary:**

- balance
- equal
- equation
- expression
- value

**Special materials needed:**

- balance scales (per pair or group)
- counters