# Lesson 7

Compose a Larger Unit

### Lesson Purpose

The purpose of this lesson is for students to add two-digit numbers and three-digit numbers and compose a ten or a hundred. Students relate composing a hundred to composing a ten.

### Lesson Narrative

In previous lessons, students used their understanding of place value to add and subtract within 100 by composing and decomposing tens. Students learned that a hundred is a unit that is composed of 10 tens and composed and decomposed hundreds to name the values of base-ten blocks.

In this lesson, the number choices and the use of base-ten blocks encourage students to look for ways to add by place and to anticipate where composing a unit might be needed before adding (MP7).

• Representation

### Learning Goals

Teacher Facing

• Add numbers within 1,000 using place value strategies that include composing a ten or hundred.

### Student Facing

• Let’s add three-digit numbers and compose tens or hundreds.

### Required Materials

Materials to Gather

Materials to Copy

### Required Preparation

Activity 2:

• Create a set of cards from the blackline master so that each student will receive 1 card.

### Lesson Timeline

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

### Teacher Reflection Questions

In previous lessons, students were encouraged to make sense of computation methods based on counting on by place that did not explicitly compose a ten or hundred. How did students demonstrate their understanding of hundreds, tens, and ones as units in today's lesson? What evidence have you seen from students that demonstrates an understanding of composing a hundred when adding?

### Suggested Centers

• Five in a Row: Addition and Subtraction (1–2), Stage 7: Add within 1,000 without Composing (Addressing)
• Number Puzzles: Addition and Subtraction (1–4), Stage 4: Within 100 with Composing (Supporting)

### Print Formatted Materials

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