The purpose of this activity is to introduce students to a new unit, the hundred. Students used connecting cubes to make tens in grade 1 and used tens and ones to count to and represent numbers within 120.

In an earlier unit, students were introduced to base-ten blocks and used base-ten diagrams to represent sums and differences within 100. Students build on this understanding as they use blocks to represent a starting number (96) and add ones until they reach a total value of 100. As students discover they have 10 tens, monitor for language they use to describe the total value of the blocks and the connections they make to their previous work with ones, tens, and three-digit numbers (MP7).

• Invite previously identified students to share how they know the value of Andre’s blocks is 100.
• “Si Andre usó el menor número posible de bloques, ¿cuántas decenas usó?” // “If Andre used the fewest number of blocks, how many tens did he use?” (He had 10 tens.)
• “Si Andre quisiera usar el mayor número posible de bloques para mostrar este número, ¿qué podría hacer?” // “What if Andre wanted to use the greatest number of blocks to show this number? What would he do?” (He’d decompose all the tens to use only ones. He’d use 100 ones.)
• “En esta actividad, ustedes mostraron que saben que 10 unidades es lo mismo que 1 decena. De la misma manera que 10 unidades es lo mismo que 1 decena, 10 decenas es lo mismo que 1 centena” // “In this activity, you showed you know that 10 ones is the same as 1 ten. Just like 10 ones is the same as 1 ten, 10 tens is the same as 1 hundred.”
• “Una centena es una unidad en base diez que está formada por 10 decenas” // “A hundred is a unit that is made up of 10 tens.”

The purpose of this activity is for students to make sense of 100 when represented as 100 ones, 10 tens, or 1 unit of a hundred with base-ten blocks or base-ten diagrams. Students compare different ways to describe 100 and connect the descriptions to base-ten diagrams (MP7). Students understand that a hundred is made up of 10 tens and can also be thought of as a unit of 100 ones.

• “¿Cómo decidiste cuál afirmación correspondía a cada diagrama?” // “How did you decide which statement matched each diagram?”
• “¿En qué se parecen estos diagramas? ¿En qué son diferentes?” // “How are these diagrams the same? How are they different?”

• “¿Cómo supieron cuál diagrama mostraba la manera en que Lin vio los bloques?” // “How did you know which diagram showed the way Lin saw the blocks?” (Lin said she saw 1 hundred, so she was thinking about the whole thing as a unit.)
• Invite previously identified students to share how they represented .
• “¿De qué manera pueden representar el 100 de la expresión con el menor número posible de bloques?” // “How could you represent the 100 in the expression with the fewest blocks?” (I could use 1 hundred block.)