# Lesson 12

How Many Are Missing?

### Lesson Purpose

The purpose of this lesson is for students to compose and decompose 10 in multiple ways and find the number that makes 10 when added to a given number.

### Lesson Narrative

In a previous lesson, students matched equations to compositions and decompositions of 10. In the first activity, students show many different compositions and decompositions of 10 with red and yellow counters. Students may know 5 and 5 as a way to compose and decompose 10, because this structure is highlighted when using fingers and 10-frames. In this lesson, students develop familiarity with other ways to compose 10. In the second activity, students determine how many counters are needed to fill a 10-frame.

- Engagement

- MLR8

### Learning Goals

Teacher Facing

- Find the number that makes 10 when added to a given number.
- Match equations to compositions and decompositions of 10.

### Student Facing

- Let’s fill 10-frames in different ways.

### Required Materials

Materials to Gather

### Required Preparation

Activity 1:

- Each group of 2 needs 1 cup and 10 two-color counters.

Activity 3:

- Gather materials from:
- Shake and Spill, Stages 1–3
- Counting Collections, Stage 1
- Roll and Add, Stages 1 and 2

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 10 min |

Activity 2 | 10 min |

Activity 3 | 25 min |

Lesson Synthesis | 5 min |

Cool-down | 0 min |

### Teacher Reflection Questions

Reflect on your experience with the Which One Doesn’t Belong warm-up in the curriculum. What moves or questions have improved the learning for each or your students during this routine? What improvements would you make next time?