# Lesson 9

Solving Problems about Proportional Relationships

### Lesson Narrative

In the previous two lessons students have been comparing proportional and nonproportional relationships using tables and equations. In this lesson they learn to recognize proportional relationships from descriptions of the context. This lesson includes the first Info Gap activity students encounter in the grade 7 course. In the Info Gap activity, students keep asking questions until they get all the information needed to solve the problem (MP1, MP6). In this case, that means they must determine if there are quantities in a proportional relationship they can work with. They see the connection between the constant of proportionality and a constant rate in the situation, and they compare different proportional relationships using the constant of proportionality. They reason quantitatively about situations and connect their reasoning with the equation for a proportional relationship (MP3).

### Learning Goals

Teacher Facing

• Decide whether it makes sense to represent a situation with a proportional relationship, and explain (orally) the reasoning.
• Determine what information is needed to solve a problem involving proportional relationships. Ask questions to elicit that information.
• Write an equation to represent a proportional relationship, and use the equation to solve problems about the situation.

### Student Facing

Let’s solve problems about proportional relationships.

### Required Preparation

Make 1 copy of the Info Gap blackline master for every 2 students, and cut them up ahead of time.

### Student Facing

• I can ask questions about a situation to determine whether two quantities are in a proportional relationship.
• I can solve all kinds of problems involving proportional relationships.

Addressing

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