Tell students to close their books or devices (or to keep them closed). Arrange students in groups of 4 and distribute pre-cut cards. Allow students to familiarize themselves with the representations on the cards:

• Give students 1 minute to place all the cards face up and start thinking about possible ways to sort the cards into categories.

• Pause the class and select 1–3 students to share the categories they identified.

• Discuss as many different categories as time allows.

Attend to the language that students use to describe their categories and graphs, giving them opportunities to describe their graphs more precisely. Highlight the use of terms like “slope,” “scale,” and “constant of proportionality.” If necessary, remind students that the constant of proportionality is the number that values for one quantity are each multiplied by to get the values for the other quantity. After a brief discussion, invite students to open their books or devices and continue with the activity.

Arrange students in groups of 2. Provide access to straightedges.

Use MLR6 Three Reads to support reading comprehension and sense-making about this problem. Display only the problem stem and the graphs, without revealing the questions.

• In the first read, students read the problem with the goal of comprehending the situation. 

  Read the problem aloud while everyone else reads along, and then ask, “What is this situation about?” Allow 1 minute to discuss with a partner and then share with the whole class. A typical response may be, “Two large water tanks are filling with water. One of them is filling at a constant rate, while the other is not. Both graphs represent Tank A. Tank B only has an equation.” Listen for and clarify any questions about the context.

• In the second read, students analyze the mathematical structure of the story by naming quantities.

  Invite students to read the problem aloud with their partner, or select a student to read to the class, then prompt students by asking, “What can be counted or measured in this situation?” Give students 30 seconds of quiet think time, followed by another 30 seconds to share with their partner. A typical response may be “liters of water in Tank A; liters of water in Tank B; amount of time that has passed in minutes; constant rate of 1/2 liters per minute.”

• In the third read, students brainstorm possible solution strategies to answer the questions.

  Invite students to read the problem aloud with their partner, or select a different student to read to the class. After the third read, reveal the first question on sketching and labeling a graph for Tank B on each of the axes and ask, “What are some ways one might solve this?” Instruct students to think of ways to approach the questions without actually solving. Give students 1 minute of quiet think time followed by another minute to discuss with their partner. Invite students to name some possible strategies referencing quantities from the second read. Provide these sentence frames as partners discuss: “To draw a graph for Tank B, I would . . . .” “One way to approach the question about finding the time when the tanks have the same amount of water would be to . . . .” and “I would use the first/second graph to find . . . .”

  As partners are discussing their solution strategies, select 1–2 students to share their ideas with the whole class. As students are presenting their strategies to the whole class, create a display that summarizes the ideas for each question.

Give students time to complete the rest of the activity followed by a whole class discussion.