Lesson 12

•  Display one statement.
• “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time.

• Share and record answers and strategy.
• Repeat with each statement.

• “How can you explain your answer for the last equation using what you know about tens and ones?” (There are only 4 tens on the right.)

The purpose of this activity is for students to interpret and solve two-step problems involving length. After reading each story problem, students consider what questions could be asked and what information will be needed in the second part of the problem. Students read each story with a partner, and then solve each story problem independently and compare their solutions.

Students begin the activity by looking at the first problem displayed, rather than in their books. Students represent the problem in a way that makes sense to them and share different representations during the synthesis, explaining how these representations helped solve the problem (MP1, MP2, MP3).

This activity uses MLR6 Three Reads. Advances: reading, listening, representing

• Groups of 2
• Give each group access to base-ten blocks.
• “The students in Priya’s class are sharing ribbons to make necklaces and bracelets for their friends and family members.”

MLR6 Three Reads

• Display both parts of the story, but only the problem stems, without revealing the questions.
• “We are going to read this problem 3 times.”
• 1st Read: “Lin found a piece of ribbon that is 92 cm long. She gave Noah a piece that is 35 cm. Then, Lin gave Jada 28 cm of ribbon.”
• “What is this story about?”
• 1 minute: partner discussion
• Listen for and clarify any questions about the context.
• 2nd Read: “Lin found a piece of ribbon that is 92 cm long. She gave Noah a piece that is 35 cm. Then, Lin cut off 28 cm of ribbon for Jada.”
• “Which lengths of ribbon are important to pay attention to in the story?” (length of ribbon Lin started with, length of ribbon given to Noah, length of ribbon given to Jada, length of ribbon Lin has in the end)
• 30 seconds: quiet think time
• 1–2 minutes: partner discussion
• Share and record all quantities.
• Reveal the questions.
• 3rd Read: Read the entire problem, including the questions, aloud.
• “What are different ways we could represent this problem?” (tape diagram, equations)
• 30 seconds: quiet think time
• 1–2 minutes: partner discussion

• “Read the story again with your partner. Then decide how to represent and solve it on your own.”
• “When you have both answered the questions, compare to see if you agree.”
• 10 minutes: partner work time
• Monitor for students who represent each part of the story with:
  • tape diagrams
  • base-ten diagrams
  • other clearly-labeled drawings or diagrams
  • equations

• Invite 2–3 previously identified students to display their work side-by-side for all to see.
• “How does each representation help you understand the problem?” (In the diagrams, they used labels to show what each part means. I can see how they used Lin's length of ribbon in both parts. In the equations, I can see the same numbers, but it's a little harder to tell what each part means. I can make sense of them by looking at the other diagrams people made.)

• Groups of 2
• Give students access to base-ten blocks.

• “Read each problem with your partner and solve it on your own. Show your thinking using diagrams, equations, or words.”
• 5 minutes: independent work time
• 5 minutes: partner discussion
• Monitor for students who use tape diagrams, base-ten diagrams, and equations to represent each part of the last problem.

Students may represent and solve the first part of each problem accurately, but see the second part as a problem with two unknowns. Consider asking:

• “What new information does the second part of the problem give you? What do you need to figure out? What do you already know?”
• “What happened in the first part of the story? What did you figure out? How could you use that in the second part of the problem?”

• Invite previously identified students to share their diagrams and equations for each part of the problem.
• “How did _____ represent the problem? How does each representation show the story problem?”