Mathematical goals

This lesson unit is intended to help you assess how well students are able to work in the coordinate plane to solve a problem in a real-world context. In particular, this unit aims to identify and help students who have difficulty measuring and interpreting horizontal or vertical intervals on graphs. This is needed later, when interpreting slope.

Introduction

This lesson unit is structured in the following way:

• Before the lesson, students work individually on an assessment task designed to reveal their current understanding and difficulties. You review their responses and create questions for them to consider when improving their work.
• After a brief introduction, students work collaboratively in small groups interpreting a graph. They then exchange their interpretation with a group that worked on a different graph. Each group sketches the other group’s interpretation as a graph. Students then share their work.
• In a whole-class discussion, students review what they have learned.
• In a follow-up lesson students use their learning and your questions to review their work.

Materials required

• Each student will need a copy of the assessment tasks A Growth Graph and A Growth Graph (revisited).
• Each small group of students will need a pair of scissors and at least one sheet of graph paper, either a copy of the sheets Vending Machine Graph: Monday and Vending Machine Cards: Monday, or the equivalent for Tuesday; the sheets Vending Machine Graph For _ _ _ _ _ (day) and Blank Vending Machine Cards; a few cut-up Completed Cards: Monday and Completed Cards: Tuesday sheets. These may be cut up or left whole, as you prefer.

• There is a projector resource to support whole-class discussions.

Time needed

20 minutes before the lesson, a 60-minute lesson, and 20 minutes in a follow-up lesson. Timings are approximate and will depend on the needs of the class.