Lesson 28

This warm-up prompts students to familiarize themselves with the mathematical context for the lesson, and builds curiosity about what kinds of objects they might be able to count in their own classroom. Teachers may use the image but it is preferable to have students answer the questions based on their own classroom. The sample responses are for the image in the workbook. Student responses will differ if they use their own classroom.

• Groups of 2
• If needed, display the image.
• “What do you notice? What do you wonder?”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Share and record responses.

• “What are some things you could count in the classroom image?” (Chairs, designs on the wall, books in the bookcase)
• “Look around our classroom. What are some things we have more than five of?” (scissors, books, desks, chairs, glue sticks, paper, markers, students)
• Record responses.
• “Do we have more than ten of any of these? How do you know?“ (There are 25 kids in the class and I know we all have a pair of scissors. So that’s more than 10. Or there are 7 table baskets and there are lots more baskets in the classroom than that.)

The purpose of this activity is for students to generate, articulate, and solve their own addition and subtraction problems. They use the context of classroom objects to create story problems and represent their thinking (MP2). Students may tell a story without asking a question, so in the launch students consider a questionless word problem so the teacher can emphasize the importance of having a question when students write their own problems.

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.
• Display and read the questionless story problem.
• “What is this story missing? What kind of questions could you ask?” (How many pencils did they have altogether? How many more pencils does Noah have than Elena?)
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share and record responses.
• “We have been solving different kinds of story problems. Today, you and your partner will write and solve addition and subtraction story problems using objects we have in our classroom.”

• “Partner A will pick a number less than 20. Partner B will use objects in the room to write a story problem and ask a question for which the number Partner A picked is the answer.”
• “Together, solve the story problem and write an equation.”
• “Switch roles for problem 2.”
• 10 minutes: partner work time
• Monitor for a variety of methods students use to add three numbers such as:
  • Count on
  • Make a 10
  • Use related facts

• “What were some of the problems you came up with that you were proud of?”
• Share students' story problems. 

The purpose of this activity is for students to create a poster of their story problem so that others can solve it. Students use these posters in the next activity, in which they solve, and write equations for other students’ story problems. They notice connections between the equation and the written problem and create a poster that communicates their work.

Alternatively, to make this task more challenging, students can rewrite their stories as missing addend story problems.

• Groups of 2
• Give each group tools for creating a visual display.
• “Now we’re going to use your story problems from the last activity to make posters so we can show our thinking and challenge each other.”

• “Choose one of the story problems you and your partner wrote. Create a poster with your story problem. Your classmates will solve it in the next activity. So make sure to not include the answer.”
• 5 minutes: partner work time.
• “Take turns sharing your poster with another pair at your table.”
• “The pair listening should tell the presenters if their poster is clear and organized.”
• 5 minutes: group work time.
• If needed, give students an opportunity to revise their posters.

• “What were some things you changed to make your poster clear and organized for the gallery walk?” (We wrote the story problem bigger. We added a picture to go with my story.)

The purpose of this activity is for students to solve their classmates’ story problems. Students may use any method that makes sense to them to solve the addition and subtraction story problems.

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.
• Set up posters in an accessible way for all students.

• “You will go around the room and read your classmates’ story problems. Then solve and write equations for them.”
• 8 minutes: gallery walk

• “Let’s reflect on the work we did today.”