Lesson 9

The purpose of this Choral Count is to invite students to practice counting by 1 from 90 to 120 and notice patterns in the count. Keep the record of the count displayed for students to reference throughout the lesson. When students notice the patterns in the digits after counting beyond 99 and explain the patterns based on what they know about the structure of the base-ten system, they look for and express regularity in repeated reasoning (MP7, MP8). Students will develop an understanding of a hundred as a unit and three-digit numbers in grade 2.

• “Cuenten de 1 en 1, empezando en 90” // “Count by 1, starting at 90.”
• Record as students count.
• Stop counting and recording at 120.

• “¿Qué patrones ven?” // “What patterns do you see?”
• 1-2 minutes: quiet think time
• Record responses.

• “¿Qué observan sobre los números que contamos?” // “What do you notice about the numbers we counted?" (Some only have two digits and some have three. After 100, I see the numbers 1–20 again.)

The purpose of this activity is to count groups of between 95 and 120 length units and represent the count using representations of tens and ones. Each group measures a strip of tape using base-ten cubes. They determine how to count the cubes and create a representation. Students may group their cubes and count by tens and ones. Some students may group 10 tens as 100. 

• Put strips of tape on the floor, 2–3 of each length. Label with the animal name. There should be one length of tape for each group of 3.
  • Beaver: 95 centimeters
  • Snake: 105 centimeters
  • Giant Anteater: 120 centimeters
  • Dog: 110 centimeters
  • Raccoon: 100 centimeters
  • Red Fox: 115 centimeters
• Make bags or buckets of about 125 base-ten cubes per group of 3.

• Groups of 3
• Give each group base-ten cubes.
• Assign each group to a strip of tape.

• “Alrededor del salón hay cintas que muestran la longitud de varios animales. Cada grupo va a medir un animal y a determinar cómo contar los cubos. Muestren cómo pensaron. Usen dibujos, números o palabras” // “Around the classroom are strips of tape that show the lengths of different animals. Each group will measure one animal and determine how to count the cubes. Show your thinking using drawings, numbers, or words.”
• 8 minutes: small-group work time

If students write the measurement as a number of tens and ones (10 tens 5 ones), consider asking:

• “¿Cómo podrías escribir este número usando solamente dígitos?” // “How could you write this number just using digits?”
• “¿Cómo dirías el número que corresponde al número total de cubos?” // “How would you say the number that matches the total number of cubes?”
• “¿Cuál número de nuestro conteo grupal corresponde al número de cubos?” // “Which number from our choral count matches the number of cubes?”

• Display 11 towers of 10 and 3 single cubes.
• “Estos son los cubos que se usaron para medir otro animal. ¿Cómo podemos descifrar la longitud de este animal?” // “These are the cubes used to measure a different animal. How can we figure out the length of this animal?”

The purpose of this activity is for students to write numbers between 95 and 120. Groups create posters that show a drawing of how they counted their animal measurements from the last activity. Groups should not write a number for the final measurement on the poster. Students do a gallery walk to interpret each representation and record the count with a number in their workbooks. Group members then compare their counts and written numbers.

When students look at the different representations and determine the length of each animal, they may notice that the representation may help to accurately find the value. For example, students may draw groups of 10 cubes rather than every individual cube (MP7).

This activity uses MLR7 Compare and Connect. Advances: representing, conversing.

• Groups of 3
• Give each group tools for creating a visual display. 

• “Creen un póster que muestre cómo contaron los cubos que usaron para medir la longitud del animal en la actividad de medir animales. No escriban en su póster el número de cubos que midió su animal” // “Create a poster to show how you counted the cubes you used to measure the length of the animal in the measuring animals activity. Do not write the number of cubes your animal measured on your poster.”
• 5 minutes: group work time
• “Ahora vamos a hacer un recorrido por el salón para ver diferentes representaciones de sus medidas. Mientras examinan cada póster, usen la representación para determinar la longitud del animal. Escriban en su libro el número de cubos que representa la longitud del animal” // “Now we will do a gallery walk to see different representations of your measurements. As you look at each poster, use the representation to determine the length of the animal. Write the number of cubes that represents its length in your book.”
• 7 minutes: gallery walk

• Display the snake and giant anteater posters.
• “¿Cómo escribo el número que representa la longitud de la serpiente?” // “How do I write the number that represents the length of the snake?”
• “¿En qué parte del póster ven 100? ¿En qué parte ven 5?” // “Where do you see 100 in this poster? Where do you see 5?”
• Repeat for giant anteater.