# Lesson 1

¿Cómo componemos una centena?

### Lesson Purpose

The purpose of this lesson is for students to make sense of a hundred as a unit composed of 10 tens or 100 ones.

### Lesson Narrative

In grade 1, students were introduced to a ten as a unit made of 10 ones. They used that understanding to represent two-digit numbers and add within 100. Students used connecting cubes to make and break apart two-digit numbers. In previous units in grade 2, students used the words compose and decompose as they made and broke apart tens when they added and subtracted within 100.

In this lesson, students are introduced to the unit of a hundred. Building on the understanding that they can use 10 ones to compose a ten, students learn they can compose a hundred using 10 tens.

• Engagement
• MLR8

### Learning Goals

Teacher Facing

• Recognize that each hundred is composed of 100 ones or 10 tens.

### Student Facing

• Compongamos una centena.

### Required Materials

Materials to Gather

### Required Preparation

Activity 2:

• Each group of 2 students needs access to at least 1 hundred block.

Building Towards

### Lesson Timeline

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

### Teacher Reflection Questions

What unfinished learning or misunderstandings do your students have about composing tens and place value? How did you leverage those misconceptions in a positive way to further the understanding of the class?

### Suggested Centers

• Greatest of Them All (1–5), Stage 1: Two-digit Numbers (Supporting)
• Mystery Number (1–4), Stage 1: Two-digit Numbers (Supporting)