Lesson 2

The purpose of this Number Talk is to elicit strategies and understandings students have for adding and subtracting 0 and 1. These understandings help students develop fluency with the count sequence and adding and subtracting within 5.

When students use their knowledge of the count sequence when they add or subtract 1, they look for and make use of structure (MP7).

• 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 strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• Display \(3 + 0\) and \(2 - 0\).
• “What is the same about these expressions? What is different about them?” (One is addition and one is subtraction. They both have zero.)

The purpose of this activity is for students to count their collection in a way that makes sense to them and keep track of which objects have been counted. Keeping track of which objects have been counted helps students count accurately and ensure they count all of the objects and do not count each object more than once (MP6). Students are provided with 10-frames and counting mats to help them organize their collections. 

• Each student needs a collection of 11-20 objects.

• Groups of 2
• Give each student a collection of objects and access to 10-frames and a counting mat.
• “How many objects are in your collection?”

• 5 minutes: independent work time
• Monitor for students who use the 10-frame or the counting mat to organize and count their objects.
• “Tell your partner how many objects are in your collection.”
• 1 minute: partner discussion

If students count each object more than once or do not count some of the objects, consider asking:

• “How many objects do you have? How do you know?” 
• Display the counting mat or the 10-frame and ask “How can you use this mat to help you make sure that you count each object?”

These students may benefit from the next activity in this optional lesson.

• Invite previously identified students to share how they counted their collections.
• “What do you notice about how they counted?” (They said one number for each object. They used the counting mat/10-frame to organize their objects. They counted all of the objects one time.)
• After each student shares, write or display the number and say, “There are _____ objects in their collection.”

The purpose of this activity is for students to practice keeping track of the objects that have been counted as they count collections of up to 20 objects. Students may benefit from working on the concepts in this optional activity more than one time.

• Each student needs a collection of 11–20 objects.
• Students need the 10-frames and counting mats from the previous activity.

• Groups of 2
• Give each student a collection of objects and access to 10-frames and a counting mat.
• Display a 10-frame mat and a counting mat.
• “How can you use the counting mat to help you figure out how many objects are in your collection?” (I can put all of the objects on one side and say a number as I move each object to the other side.)
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• Share responses.
• “How can you use the 10-frame to help you figure out how many objects there are in your collection?” (I can put one object in each box and line up the rest of the objects. Then I can count them.)
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• Share responses.
• “Choose either the 10-frame or the counting mat to help you figure out how many objects are in your collection.”

• 4 minutes: independent work time
• “Find a partner who used a different tool to help them count their collection. If you used a 10-frame to help you count your collection, find a partner who used the counting mat. Show your new partner how you counted your collection.”
• 4 minutes: partner work time

• Invite at least one student who used each tool to share how they counted their collection.
• After each student shares, write or display the number and say, “There are _____ objects in their collection.”
• “How do you know that you have counted each object one time?” (I moved the objects from one side of the counting mat to the other. There are none left on this side, so I counted them all. I put them in a 10-frame and then touched and counted each one in order.)
• If needed, “When we count, a counting mat or 10-frame can help us make sure that we count each object 1 time.”

The purpose of this activity is for students to choose from activities that offer practice with addition, subtraction, and tracing numbers.

Students choose from any stage of previously introduced centers.

• Number Race
• Subtraction Towers
• 5-frames

• Gather materials from:
  • Number Race, Stages 1 and 2
  • Subtraction Towers, Stage 1
  • 5-frames, Stages 1 and 2

• “Today we are going to 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

• “When did you see a classmate count during centers today?”