Lesson 13

This warm-up prompts students to carefully analyze and compare features of tape diagrams and equations. In making comparisons, students have a reason to use language precisely (MP6). The activity also enables the teacher to hear the terminologies students know and how they talk about characteristics of tape diagrams and connect them to equations (MP2, MP7).

• Groups of 2
• Display image.
• “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 2–3 minutes: partner discussion
• Share and record responses.

• “Let’s find at least one reason why each one doesn’t belong.”
• “Which diagram best matches the equation in C? Explain.”

The purpose of this activity is for students to connect story problems to the equations that represent them and to solve different types of story problems. Students identify equations with a symbol for the unknown that match a story problem and justify their decisions by describing how the equations represent the quantities and any actions in the story problem (MP4). When students analyze and connect the quantities and structures in the story problems and equations, they are thinking abstractly and quantitatively (MP2) and making use of structure (MP7).

• Create a set of cards from the blackline master for each group of 2–4.
• Each group of 2–4 needs a set of cards from the previous lesson.

• Groups of 2–4
• Give each group the story problems (Cards A–I) from the Story Problem and Diagram Cards.
• Give one set of Equation Cards to each group of students.
• Give each group access to base-ten blocks.
• “Take turns reading the story problems. After one person reads, work together to find an equation that matches. When you think you have found a match, explain to your group why the cards match.”
• “If you think that more than one card could match the story, explain the match to your group.”
• As needed, demonstrate the activity with a student volunteer.
• “When your group finishes, choose 2 story problems from Cards F, G, H, or I and solve them.”

• 6 minutes: partner work time
• Monitor for students who explain why more than one equation may match a story and how the equations match the quantities in the context of the story problem.
• 4 minutes: independent work time

Students may believe that only one equation could match each story. Encourage students to describe how equations match any actions in the story and whether any other equations show the same actions. If there are no actions in the story, ask students to explain why one or more cards shows the relationship between the parts and the whole. Consider providing the tape diagrams from the previous activity to support students in their explanations.

• Invite students to share a match for each story. 
• Consider asking:
  • “How does the equation match the story problem?”
  • “Is there another equation that could match the story problem? Explain why or why not.”

The purpose of this activity is for students to use tape diagrams and equations to represent different types of story problems within 100. In this activity, students interpret story problems and use diagrams and equations to represent the unknown quantities. Students are encouraged to solve using a method that makes sense to them.

Students may complete the parts of each problem in an order that makes sense to them. In the synthesis, students compare and connect their diagrams, equations, and methods for solving (MP2, MP7). Monitor for students who draw accurate diagrams and create different equations for the problem with Noah and Kiran’s seeds to share in the lesson synthesis.

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

• “Now you get a chance to draw diagrams and write equations that represent story problems.” 
• “Read the story carefully. Then solve each problem and show your thinking.”
• 8 minutes: independent work time
• 5 minutes: partner discussion
• Monitor for students who: 
  • use an addition equation to represent Andre’s seeds
  • subtract to find the number of seeds Andre won using a base-ten diagram or equations.

If students draw their own diagrams, but do not label the quantities, consider asking:

• “What are the different things that you can count in the story? How does your diagram show these things?”
• “What could you add to your diagram to help someone make connections to the story?”

• Invite a previously identified student to share their completed tape diagram and the addition equation for Andre's seeds.
• Invite a previously identified student to share the way they used subtraction to find how many seeds Andre won.
• “How are _____’s equation and _____’s method the same? How are they different?” (They both use the same numbers. _____’s method is a way to find the unknown value in the equation. They are different because the equation is addition, but the method shows subtraction).
• “Does _____’s method using subtraction match the actions in the story problem? Explain why or why not.” (No. The story tells about starting with some seeds and getting more seeds. That is addition. But you can use subtraction to find the value, since there is an unknown addend.)
• “Sometimes it might be better to use addition or subtraction equations to represent the actions that are happening in a story. But you can always use addition or subtraction to find an unknown addend.”