The purpose of this activity is for students to separate objects into groups of 2 and identify numbers of objects that can be split into pairs with “no leftovers” and numbers of objects that can be split into pairs with “one leftover.” In the Activity Synthesis, create a t-chart with students that lists the numbers that belong to each category. Students share what they notice and wonder about each group of numbers. Save the t-chart for use in the Lesson Synthesis.

When recording student responses, show how students counted to find the total number of counters by drawing pairs in rows (see Activity Synthesis). This helps students see the groups of 2 and prepares them for analyzing arrays in future lessons.

This activity uses MLR8 Discussion Supports. Advances: speaking.

• Display t-chart labeled “Formemos parejas” // “Making Pairs” with “no sobran” // “no leftovers” and “sobra una” // “one leftover” as the categories.
• Invite students to share a total amount and whether they made pairs with no leftovers or pairs with a leftover.
• Record the total on the chart.
• “¿Cómo contaron las fichas para encontrar el total?” // “How did you count the counters to find the total?” (I counted each pair by 2.)
• Represent how the student counted by drawing dots in rows. If students count by 2, represent this by drawing two dots at a time and count by 2.
  • For example:

    

• “Observen los números de cada columna. ¿Qué observan? ¿Qué se preguntan?” // “Look at the numbers in each group. What do you notice? What do you wonder?” (All of the numbers show pairs. The numbers in the leftover group have only 1 leftover, and the rest make pairs. I wonder what other numbers go in these groups. I wonder if these are the same numbers we found had 1 leftover yesterday.)

• Before students share, remind them to use words, such as “parejas” // “pairs,” “grupos iguales” // “equal groups,” and “que sobran” // “leftovers.”
• 1 minute: quiet think time
• 1-2 minutes: partner discussion
• Share responses.
• If needed, ask, “Al formar parejas para cada número, ¿cuántas sobraron?” // “How many leftovers did each number have?”

The purpose of this activity is for students to determine whether a group of people (16–20) can be organized into groups of 2 without any person left out of a group or any groups of 3. Students begin to reason about whether a group of objects is even or odd by using what they know about counting or adding by 2 (MP7, MP8). Students should be given access to counters, but they may use other representations, including equations.

• Draw or display:

• “¿Cómo podemos mostrar con esta representación que todos los estudiantes de la clase de Noah tendrán un compañero?” // “How could we use this representation to show whether everyone in Noah’s class will have a partner?” (There are 18 circles and you can see they are in pairs. 19 is 1 more than 18. So, 1 circle would not be in a pair.).
• Share responses. Include reasoning and representations for 19 from previously selected students.