Lesson 9

The purpose of this Choral Count is to invite students to count to 19 and notice patterns in the count. Recognizing these patterns may help students remember how to write teen numbers. Students often reverse the digits due to how we say the teen numbers.

• “Count by ones, starting at 0.”
• Record as students count.
• Stop counting and recording at 19.

• “What patterns do you see?”
• 1–2 minutes: quiet think time
• Record responses.

• “If we wanted to count on from 10, what number would we say after 10? How do you know?” (11 because 11 is one more than 10 and comes after 10 when we count.)

The purpose of this activity is for students to make connections between written numbers and expressions. In the activity synthesis, students see each teen number written as an equation. In this unit, when reading equations to students, read the equal sign as “is.” For example, read \(10 + 3 = 13\) as “10 plus 3 is 13.” The equal sign will be read as “equals” in the next unit.

• Create a set of cards from the blackline master for each group of 4.

• Groups of 4
• Give each group of students a set of cards.
• “Work with your group to organize the cards in a way that makes sense to you.”

• 6 minutes: small-group work time
• Monitor for students who organize the numbers and expressions as shown in the sample response.

• Invite a group of students to share how they organized the numbers and expressions or display the image in student responses.
• “What do you notice about the numbers and expressions when they are arranged this way?” (They’re in the order that we count. The first number stays the same. The second number is 1 more each time. All the expressions have a 10. The second number starts at 1 and is one more each time. The expressions match the numbers.)
• “Which number does \(10 + 1\) represent? How do you know?” (11)
• “\(10 + 1\) is 11. We can write that as \(10 + 1 = 11\).”
• Demonstrate writing equations for each number and expression.

The purpose of this activity is for students to match equations to numbers 11–19 presented on 10-frames. During the synthesis, students focus on each part of the equation and where it can be seen in the 10-frame representation of the number. When students see different parts of the equations in the 10-frame images, they look for and make use of structure (MP7).

• Groups of 2
• “Draw a line from each equation to the dots it matches.”

• 2 minutes: independent work time
• 3 minutes: partner work time

• Invite a student to share which image matches \(10 + 5 = 15\).
• “Where do you see 15 on the 10-frame?” (There are 15 dots altogether.)
• “Where do you see \(10 + 5\) on the 10-frame?” (There are 10 dots on the 10-frame and 5 dots under the 10-frame.)

The purpose of this activity is for students to learn stage 2 of the Make or Break Apart Numbers center. Students find 2 groups on their gameboard that make a given number and record the composition with an expression. After they participate in the center, students choose from any stage of previously introduced centers.

• Bingo
• Number Race
• Grab and Count 
• Tower Build

Gather materials from:

• Bingo, Stages 1-4
• Number Race, Stages 1 and 2
• Grab and Count, Stage 1
• Tower Build, Stages 1 and 2

• Groups of 2
• Give each group of students two-color counters, 1 connecting cube, and a number mat. Give each student a recording sheet and a gameboard.
• “We are going to learn a new way to do the Make or Break Apart Numbers center.” 
• “I’m going to roll a cube onto the number mat to find which number I have to make.”
• Demonstrate rolling the connecting cube onto the number 13.
• Display the gameboard. 
• “We rolled the number 13. My partner and I have to find 2 groups that go together to make 13. Which groups go together to make 13?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.
• “I’m going to put a counter on this group of 10 dots and a counter on this group of 3 fingers. 10 and 3 is 13. What expression should I write on my recording sheet?” (\(10 + 3\))
• 30 seconds: quiet think time
• Share responses.
• Demonstrate writing \(10 + 3\).
• “Now that my partner and I have written our expression, we can look to see if there are 2 more groups that go together to make 13. If we can’t find any more ways to make 13, then we roll and make another number.”
• “Take turns with your partner to find 2 groups to make a number and write an expression.”

• 8 minutes: partner work time
• “Now you can choose another center. You can also continue playing Make or Break Apart Numbers.”
• Display the center choices in the student book.
• Invite students to work at the center of their choice. 
• 10 minutes: center work time

• “We worked with numbers 11-19 in centers. Tell your partner two things that you know about these numbers.”