The purpose of this activity is for students to revisit Stage 2 of the Counting Collections center. In this activity, students organize, count, and represent a collection of 52 objects. Students should have access to double 10-frames, cups, paper plates, or other tools that can help them organize.

Students choose how to count their collection and how to represent their count. Students may count by one because they don’t trust that counting by ten yields the same result. Students may apply what they learned in previous lessons and create groups of ten using double-ten frames or other tools (MP5). Students may continue to count by one after they have organized the cubes into tens while others may count by ten, then one. Regardless of how they count, students need to be careful and organized to make sure they count accurately (MP6).

Although all students count a collection of 52 objects during this activity, when Stage 2 of the Counting Collections center is offered as a choice in later lessons, the collections should include quantities up to 99.

• Invite students to share how many objects they counted in the collection.
• “¿En qué era diferente esta colección de otras colecciones que contaron antes?” // “How was this collection different from the collections that you counted before?” (Those collections only had tens and this one has tens and some ones.)
• “Algunas colecciones de objetos se pueden organizar en grupos de 10 sin que sobren objetos. Algunas colecciones de objetos tienen grupos de 10 y algunos objetos que sobran. Algunas tienen algunas decenas y algunas unidades. Decimos que esta colección tiene 5 decenas y 2 unidades” // “Some collections of objects can be organized into groups of ten objects with no leftovers. Some collections of objects have groups of ten and some leftover objects. They have some tens and some ones. We say that this collection has 5 tens and 2 ones.”

The purpose of this activity is for students to analyze a collection of connecting cubes that are arranged in towers of 10. Students analyze another student’s thinking about a representation of 48 cubes in towers of 10. When students explain that they disagree with Noah because a ten must include 10 ones, they show their understanding of a ten and the foundations of the base-ten system (MP3, MP7).

• “¿Cómo puedes revisar si hay o no hay 50 cubos?” // “How are you checking to see if there are 50 cubes?”
• “¿Cómo puedes usar lo que sabes sobre grupos de diez para revisar cómo pensó Noah?” // “How can you use what you know about groups of ten to check Noah’s thinking?”

• Invite students to share whether they agree or disagree, and their reasons.
• “¿Cómo saben que no hay 50 cubos?” // “How do you know there aren't 50 cubes?” (50 is 5 tens. There are only 4 tens here. The last tower isn’t 10. There are 4 tens and 8 ones.)

The purpose of this activity is for students to choose from activities that offer practice adding and subtracting. Students choose from any of the previously introduced stages of the centers. They are encouraged to choose the center that will be most helpful for them at this time.

• Check It Off
• Five in a Row
• Number Puzzles

• “Jada está jugando ‘Márcalo’. Todavía tiene que marcar 30. ¿Qué números podría escoger Jada para obtener una suma o diferencia de 30?” // “Jada is playing Check It Off. She still needs to check off 30. What numbers could Jada pick to get a sum or difference of 30?” (20 and 10, 90 and 60, 80 and 50, 70 and 40, 60 and 30, 50 and 20, 40 and 10)