Lesson 1

The purpose of this warm-up is to elicit the idea that numbers can be broken into parts, which will be useful in upcoming activities. While students may notice and wonder many things about these images, the fact that they have the same number of shapes, but one is separated into 2 parts is the important discussion point.

• Groups of 2
• 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 is the same about these pictures? What is different?” (They both have 5. The first picture is 1 big group but the second picture is 2 groups.)

The purpose of this activity is for students to decompose 6 into 2 parts. Students see that the total number of cubes remains the same when it is decomposed into 2 parts. Although students may notice that they can do this in different ways, that idea is not the focus until the next activity.

• Each student needs 6 connecting cubes.

• Groups of 2
• Give each student 6 connecting cubes.

• “You have 6 cubes. Put some of the cubes in your hand and some on your desk.”
• 30 seconds: independent work time
• “Tell your partner how many cubes are in your hand. Show them the cubes.” 
• “Tell your partner how many cubes are on your desk. Show them the cubes.” 
• “Tell your partner how many cubes you have altogether.”

• Invite a student to share.
• “How many cubes did you have in your hand? How many cubes were on your desk?”
• Write an expression to represent the parts.
• “How many cubes did you have in all?” (6)
• “The total number of cubes stays the same when we break them up into 2 parts.”

The purpose of this activity is for students to see that numbers can be decomposed in different ways. Students analyze two different ways that 4 cubes are decomposed into two groups. They determine that although they are decomposed into different-sized parts, they both represent a total of 4.

• Groups of 2
• Give students access to connecting cubes.
• “Diego and Lin also put some cubes in their hands and some on their desks. Diego has 3 in his hand and 1 on his desk. He says he has 4 cubes altogether. Lin has 2 in her hand and 2 on her desk. She also says she has 4 cubes total. Can they both have 4 cubes altogether?”

• 3 minutes: partner discussion
• Monitor for students who count the groups to determine that both students have 4 even though they are broken into different parts.

• “Do Diego and Lin both have 4 cubes?”
• Invite previously identified students to share.
• “What parts did Diego break 4 into? (3 and 1)
• Write \(3 + 1\).
• “What parts did Lin break 4 into?” (2 and 2)
• Write \(2 + 2\).
• “Diego and Lin showed us that we can break numbers apart in different ways.”

The purpose of this activity is for students to learn stage 1 of the Check It Off center. Students take turns picking two number cards (0–5) to make and find the value of an addition expression. Students check off the total and then write the addition expression on the recording sheet. 

After they participate in the center, students choose from any stage of previously introduced centers.

• Find the Value of Expressions
• Bingo
• Shake and Spill

Students will choose from these centers throughout the section. Keep materials from these centers organized to use each day.

• Gather materials from: 
  • Find the Value of Expressions, Stage 1
  • Bingo, Stages 1–3
  • Shake and Spill, Stages 1–3

• Groups of 2
• Give each group of students a set of number cards and each student a recording sheet.
• “We are going to learn a center called Check It Off. You and your partner will take turns choosing two number cards. Find the total of the two numbers, and check off the total on your recording sheet. Then fill in an expression.”

• 10 minutes: partner work time
• “Now you can choose another center. You can also continue playing Check It Off.”
• Display the center choices in the student book.
• Invite students to work at the center of their choice. 
• 10 minutes: center work time

• “Choose 1 expression that you wrote on your recording sheet. Tell your partner how you can find the value of that expression.”