The mathematical purpose of this lesson is for students to review their understanding of the meaning of operations and expressions with operations on variables, and to practice extracting important information from situations. Students get multiple opportunities to connect verbal descriptions of situations and questions about those situations to expressions with variables that represent those situations. The work of this lesson connects to previous work done in grade 6, as students used variables to represent numbers and wrote expressions as they solved real-world and mathematical problems. In the associated Algebra 1 lesson, students create expressions to represent the quantities and relationships in a situation and begin to represent constraints in a situation. This lesson prepares students to begin the work in the associated Algebra 1 lesson by providing practice in thinking through the verbal descriptions of situations and helping them recall the kinds of questions that different operations help to answer. Students reason abstractly and quantitatively (MP2) as they move between doing specific calculations to answer questions, to writing a general expression that represents a situation with unknown quantities.
- Describe in words the relationships expressed by algebraic expressions.
- Represent relationships expressed in words using algebraic expressions.
- Let’s use operations and variables to describe situations.