Comparing Strategies for Proportion Problems
This lesson unit is intended to help you assess whether students recognize relationships of direct proportion and how well they solve problems that involve proportional reasoning. In particular, it is intended to help you identify those students who:
- Use inappropriate additive strategies in scaling problems, which have a multiplicative structure.
- Rely on piecemeal and inefficient strategies such as doubling, halving, and decomposition and have not developed a single multiplier strategy for solving proportionality problems.
- See multiplication as making numbers bigger and division as making numbers smaller.
This lesson unit is structured in the following way:
- Before the lesson, students work individually on a task designed to reveal their current levels of understanding and difficulties. You review their work, writing questions to help them to improve.
- During the lesson, students first work in pairs or threes on the same task. Then working in the same small groups, they analyze work produced by other students on the task.
- In a whole-class discussion, students compare and evaluate the methods they have seen and used.
- Finally, students review their initial, individual response, using their learning to complete a new similar task.
- Each individual student will need a mini-whiteboard, pen, and eraser, a calculator and a copy of the tasks A Sense of Scale and A Sense of Scale (revisited).
- Each small group of students will need a large sheet of poster paper and a copy of each of the Sample Responses to Discuss.
15 minutes before the lesson, a 60-minute lesson, and 15 minutes in a follow-up lesson. These timings are approximate. Exact timings will depend on the needs of your students.
This lesson involves a range of mathematical practices from the standards, with emphasis on:
- MP1: Make sense of problems and persevere in solving them
- MP2: Reason abstractly and quantitatively
- MP3: Construct viable arguments and critique the reasoning of others
- MP4: Model with mathematics
- MP6: Attend to precision
- MP7: Look for and make use of structure
- MP8: Look for and express regularity in repeated reasoning
Mathematical Content Standards
This lesson asks students to select and apply mathematical content from across the grades, including the content standards:
- 7.RP: Analyze proportional relationships and use them to solve real-world and mathematical problems.