Use Stronger and Clearer Each Time to give students an opportunity to revise and refine their response to “Did either of these sets of measurements determine one unique triangle? How do you know?” In this structured pairing strategy, students bring their first draft response into conversations with 2–3 different partners. They take turns being the speaker and the listener. As the speaker, students share their initial ideas and read their first draft. As the listener, students ask questions and give feedback that will help their partner clarify and strengthen their ideas and writing.
If time allows, display these prompts for feedback: 

• “ makes sense, but what do you mean when you say. . . ?”
• “Can you describe that another way?”
• “How do you know . . . ? What else do you know is true?”

Close the partner conversations, and give students 3–5 minutes to revise their first draft. Encourage students to incorporate any good ideas and words that they got from their partners in order to make their next draft stronger and clearer.

If the optional blackline master was used, ask students:

• “Which configurations made identical triangles?” (the top left and bottom left)
• “Which configurations made more than one triangle?” (the bottom right)

If not mentioned by students, explain to students that the top left and bottom left configurations result in the same triangle, because in both cases the angle is in between the 4-cm and 5-cm sides, and that the bottom right configuration results in two different triangles, because the arc intersects the ray in two different places.

If students struggle to get started, remind them of Lin’s technique of using the protractor and a ruler to make an angle that can move along a line.

Some students may draw two different orientations of the same triangle for the first set of conditions, with the angle in between the 4-cm and 5-cm sides. Prompt them to use tracing paper to check whether their two triangles are really different (not identical copies).

If students struggle to create more than one triangle from the first set of conditions, prompt them to write down the order they already used for their measurements and then to brainstorm other possible orders they could use.