# Lesson 14

Towers of 10

### Lesson Purpose

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

### Lesson Narrative

In previous lessons, students composed and decomposed 10 in multiple ways and found the number that makes 10 when added to a given number. In this lesson, students determine how many cubes are hidden when a tower of 10 connecting cubes is broken into 2 parts and only 1 part is visible. Determining how many more are needed to make 10 is more challenging with connecting cubes than with a 10-frame or fingers because students cannot use the structure of the 10-frame or fingers and simply count the empty squares or the fingers that are down. The goal of the lesson synthesis is for students to reflect on the different tools they have used to compose and decompose 10.

• Action and Expression
• MLR8

Activity 1: Introduce What’s Behind My Back?, 10 Cubes

### Learning Goals

Teacher Facing

• Find the number that makes 10 when added to a given number.

### Student Facing

• Let’s figure out how many cubes are hidden.

### Required Materials

Materials to Gather

Materials to Copy

• What's Behind My Back Stage 2 Recording Sheet Kindergarten

### Required Preparation

Activity 1:

• Each group of 2 need 20 connecting cubes.

Activity 3:

• Gather materials from:
• What's Behind My Back, Stages 1 and 2
• Math Fingers, Stages 1-4
• Shake and Spill, Stages 1-3
• Counting Collections, Stage 1
• Roll and Add, Stages 1 and 2

Building Towards

### 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. List ways you have seen each student grow as a young mathematician throughout this work. List ways you have seen yourself grow as a teacher. What will you continue to do and what will you improve on in the next unit?