Lesson objective: Fluently write equations from word problems with a letter representing unknown values.

This lesson helps to build fluency with writing equations from word problems involving measurement. Bar models are used here because it supports the visual representation of word problems which helps to translate from numbers and operations to equations. This work develops students' understanding that we can represent problems using equations with letters standing for the unknown quantity.

Students engage in Mathematical Practice 2 (represent abstractly and quantitatively) as they contextualize and decontextualize within the process of problem solving. Students make sense of the quantities and their relationship in problem situations. Students will use abstractions to represent a problem symbolically or with other mathematical representations and make connections between them.

**Key vocabulary:**

- Equation
- Unknown

**Special materials needed:**

- whiteboards
- dry erase markers
- clipboard