The purpose of this activity is for students to interpret different base-ten representations of a two-digit number. Students compare drawings to words (_____ tens _____ ones) and an expression showing the value of the tens and ones digits as a sum. One of the representations shows the ones to the left of the tens so that students think about the value of the units. One of the representations shows a base-ten diagram with the towers of ten labeled “10” rather than representing all ten cubes in each tower. It is important that students who use this type of drawing can explain that the unit of ten contains 10 ones.

• Invite previously identified students to share.
• “What connections do you see between the representations?” (Each representation shows the same amount. Each representation shows tens and ones.)
• “How are the representations alike? How are they different?" (They both show 73. Han’s shows tens and ones, but the tens don’t show all the ones. Han labels it as 10 or 1.)
• “Han’s representation is a new representation that you may want to try using to show your thinking.”

The purpose of this activity is for students to match cards that show different base-ten representations. The representations are base-ten diagrams, ___ tens ___ ones, 2-digit numbers, and addition expressions that show the value of the tens and ones digits. This sorting task gives students opportunities to analyze different base-ten representations closely and make connections (MP2, MP7). Some cards represent the ones to the left of the tens to encourage students to focus on the units and the meaning of digits. As students work, encourage them to refine their descriptions of base-ten representations using more precise language and mathematical terms (MP6).

• Invite students to share how they matched the cards.
• Listen to the language students use to describe their matches and representations, giving them opportunities to describe the representations more precisely with attention to how they show amounts of tens and ones.
• Highlight the use of terms such as “tens,” “ones,” and “digits.”

The purpose of this activity is for students to learn a new center called Grab and Count. Students grab a handful of ones cubes and put them together with their partner’s. They estimate how many cubes and then count the cubes. Students record their estimate and the actual number of cubes on the recording sheet. Since students have not written two-digit numbers yet, students may attempt to record the two-digit number or use other, more familiar, representations to show the amount of cubes.

• “How did you keep track of the cubes as you counted?” (We made groups of ten. We moved the cubes as we counted them.)