The purpose of this activity is for students to count a collection of objects and show on paper how many there are so that others can understand how they counted. This collection of objects is a teen number of connecting cubes to encourage students to unitize a ten (MP7). In the Synthesis, students consider representations that show a group of 10 cubes.

• “How did you count the objects?”
• “How can you organize the objects as you count so you know you counted each one?”

• Invite previously identified students to share in the sequence shown.
• “How are these representations alike? How are they different?” (They all show there are 16 cubes. Some show counting by ones. Some are organized in rows. Some made a group of 10 and counted on.)
• “Where is 10 in each representation?” (In _____’s representation, you see the 10 when they count up to it by ones. In _____’s representation, they circled 10 ones to show 10. In _____’s representation, they connected 10 and wrote 10 before counting on to 16.)
• “We can call a group of 10 ones a ten. These representations show a ten and 6 ones. A ten and 6 ones is the same as 16.”

The purpose of this activity is for students to compose a teen number as one ten and some ones. In the Launch, students look at an example of cubes arranged in a tower of 10 and singles. Then students build teen numbers out of connecting cubes using a tower of 10 cubes. As students share their thinking, the teacher draws a tower of 10 units and some ones. For example, a student may say, “I have a tower of ten, and made a line with the 4 other cubes, 11, 12, 13, 14.” The teacher draws: 14

If students do not specifically describe their arrangement, the teacher should ask students, “How did you arrange the ones?” before drawing them.

Some students may connect the cubes that represent ones in their representation, but it is important that the teacher draws and labels them as separate units.

• Invite previously identified students to share their representations.
• Record each with a diagram.
• “What did you notice as you were showing these numbers with connecting cubes?” (They all had a tower of 10.)
• “The numbers we made today are called teen numbers. A teen number is a number with 1 ten and between 1 and 9 ones.”