# Lesson 19

Encontremos el número con el que se forma 10 (optional)

### Lesson Purpose

The purpose of this lesson is for students to find the number that makes 10 when added to a given number.

### Lesson Narrative

Students have access to tools used throughout the year, including two-color counters, connecting cubes, fingers, 10-frames, and bead tools, to help them find the number that makes 10. With repeated experience, students may know some of the numbers needed to make 10 by memory, such as 5 and 5 or 9 and 1. Students fill in equations to represent these compositions and decompositions of 10. This lesson is optional because the standards do not require students to fill in equations with one missing addend in kindergarten.

If students need additional support with the concepts in this lesson, refer back to Unit 5, Section C in the curriculum materials.

• Engagement
• MLR8

### Learning Goals

Teacher Facing

• Fill in equations to represent compositions and decompositions of 10.
• Find the number that makes 10 when added to a given number.

### Student Facing

• Sumemos para formar 10.

### Required Preparation

Activity 1:

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

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

### 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

What opportunities are you giving students to reflect on their understanding of the mathematical content?