Lesson 13

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 100. Students may share how they use mental strategies to make a ten. When students share how they use the value of one expression to find the value of the next expression, they look for and express regularity in repeated reasoning (MP8).

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategies.
• Keep expressions and work displayed.
• Repeat with each expression.

• “What changes in the second, third, and fourth sums?” (the tens of the second number)
• “How does this help you calculate the third and fourth sums?” (I just add some more tens.)

The purpose of this activity is for students to solve their story problems and represent one or more ways to solve the problem (MP2). As students work, encourage them to find a different way to solve the problem or a different way to represent the problem once they have completed a solution.

• Groups of 2
• Give students materials to make posters. 

• “Today you are going to solve your story problem and then make a poster that shows your story problem and how you solved it.”
• “If you have time, you can show different ways to solve the problem using pictures, words, or symbols.”
• 10 minutes: independent work time
• “Share your poster with your partner and make revisions if needed.”
• 5 minutes: partner discussion

• “In the next activity, you are going to look at the posters and leave comments.”
• “What are some things that you will look for when you look at the posters?” (Do I understand the story? Do I agree with the solution? Can I follow the thinking or reasoning?)
• “What are some different ways you can show solutions to the problems?” (pictures of objects, base-ten pictures, diagrams, number line diagrams, expressions, equations)
• “Keep an eye out for all of these representations and think about which ones you would choose if you were solving the problem.”

The purpose of this activity is for students to see the different story problem posters their classmates made. After the gallery walk, students have a chance to make revisions to their own posters. This could be making corrections, but it could also be adding new details or different representations based on what they learned from seeing the other posters. Some students might need guidance with asking mathematical questions or leaving feedback using precise math language (MP3, MP6).

Consider asking or displaying:

• “What is something you read or saw that helped you understand the story problem?”
• “What is something the writer could add or change to help make the problem more clear?”
• “What is something you saw that made it clear how the problem was solved?”
• “What is something that could be added or changed to make the writer’s method more clear?”
• “What questions do you have about the story problem or the solution?”

The goal of the activity synthesis is to reflect on how the posters were the same and how they were different.

• Groups of 2
• Display student posters on tables or walls.
• Give students access to sticky notes.

• “Walk around the room with your partner and look at the posters. Talk to your partner about what you notice and what you wonder.”
• “Use your sticky notes to leave comments or questions about the stories and solutions, including things that helped you understand the problem and solutions and any other representations you might add to the poster.”
• 7 minutes: partner work time
• “Make revisions to your own poster based on what you saw and discussed.”
• 3 minutes: independent work time
• Monitor for students who may need questions or prompts to guide them with leaving feedback. 

• “What did you change on your poster after seeing the other posters?” (Answers vary.)
• “If you had time, what other changes or additions would you make?”