Lesson Objective: Practice changing quantities with like units to maintain a proportional relationship.

Students work with money to maintain a savings plan. Tape diagrams are used to represent the relationship, and students work with varying values of money while maintaining the relationship of Robbie's and his parent's contribution.

Students engage in Mathematical Practices 4 and 7 in this lesson. They model the relationship between Robbie’s savings and his parents’ contributions using a tape diagram (MP.4), ensuring that the relationships between the amounts are maintained regardless of the specific quantities being used. They also make use of structure (MP.7), noticing that there are multiple ways to derive one quantity in the relationship from the other (e.g., to find how much Robbie saved, we can multiply the parents’ contribution by ⅔ *or *divide by 3 and multiply the quotient by 2).

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