Lesson 21

Compongamos y descompongamos números del 11 al 19

Lesson Purpose

The purpose of this lesson is for students to compose and decompose numbers 11–19 using 10 ones and some more ones.

Lesson Narrative

In the first activity, students decompose groups of 11–19 objects into groups of 10 ones and some more ones. Then students determine the missing part to compose numbers 11–19.

If students need additional support with the concepts in this lesson, refer back to Unit 6, Section B in the curriculum materials.

  • Action and Expression
  • MLR8

Activity 1: ¿Dónde se van a sentar?

Learning Goals

Teacher Facing

  • Compose and decompose numbers 11–19 using 10 ones and some more ones.

Student Facing

  • Hagamos grupos de 10.

Required Preparation

Activity 1:

  • Each group of 2 needs access to at least 2 collections of 11–19 objects.

Activity 2:

  • Students can use their bead tool from a previous lesson.

Activity 3:

  • Gather materials from:
    • Shake and Spill
    • Number Race
    • Grab and Count
    • What's Behind My Back?
    • Pattern Blocks

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 15 min
Activity 2 10 min
Activity 3 20 min
Lesson Synthesis 5 min
Cool-down 0 min

Teacher Reflection Questions

As you finish up this unit, reflect on the norms and activities that have supported each student in learning math. How have you seen each student grow as a young mathematician throughout this work? How have you seen yourself grow as a teacher?

Print Formatted Materials

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Student Task Statements pdf docx
Lesson Cover Page pdf docx
Teacher Guide Log In
Teacher Presentation Materials pdf docx