Lesson 5

This warm-up prompts students to compare four images focusing on groups of 10. It gives the teacher an opportunity to hear how students use terminology and talk about characteristics of the items in comparison to one another (MP6). During the synthesis, ask students to explain the meaning of any terminology they use, such as groups of 10.

• Groups of 2
• Display the 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.”
• ”How are A and B alike?” (They both show three groups of 10.)

The purpose of this activity is for students to learn stage 2 of the Check It Off center. Students take turns picking two number cards that are multiples of 10 (0–90) and choose whether to make an addition or subtraction expression. Students check off the value of the sum or difference (0–90) and then write the addition or subtraction expression on the recording sheet.

• Create a set of cards from the blackline master for each group of 2.

• Groups of 2
• Give each group a set of cards, two recording sheets, and access to connecting cubes in towers of 10.
• “We are going to learn a new way to do the Check It Off center. It is called Check It Off, Add or Subtract Tens.”
•  “Choose two cards and decide whether you want to add or subtract. After you find the sum or difference, check it off on the recording sheet and write the expression. Take turns with your partner. At the end of the game the partner who checks off the most numbers wins.”

• 10 minutes: partner work time

• Display a recording sheet with 90 checked off and 10 not checked off. 
• Display cards 40 and 50.
• “Should we add or subtract these numbers? Why?” (We should subtract because \(50 - 40 =10\) and we haven’t checked off 10 yet, but \(40 + 50 = 90\) and 90 is already checked off.)

The purpose of this activity is for students to choose an activity to work on that focuses on addition and subtraction. Students choose from any stage of previously introduced centers.

• Five in a Row
• How Close?
• Number Puzzles

• Gather materials from previous centers:
  • Five in a Row, Stages 1–4
  • How Close, Stages 1 and 2
  • Number Puzzles, Stages 1 and 2

• Groups of 2
• “Now you will choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do first.”
• 30 seconds: quiet think time

• Invite students to work at the center of their choice.
• 10 minutes: center work time
• “Choose what you would like to do next.”
• 10 minutes: center work time

• “What is one thing you learned or got better at by working on the activity you chose?”