# Lesson 11

### Lesson Purpose

The purpose of this lesson is for students to add within 20 when one addend is a teen number.

### Lesson Narrative

In previous lessons, students learned that a teen number is composed of a ten and some ones and related addition and subtraction with teen numbers in equations. Students also learned that counting is related to addition, and added numbers using the commutative property.

The purpose of this lesson is for students to solve an addition story problems within 20 in which one addend is a teen number. Students then find the missing value in addition equations where one addend is a teen number. Students may count all, count on, or recognize that they can add the ones and then add the ten. This lesson prepares students for future work, when they add within 100 using methods involving place value.

• Engagement
• MLR7

Teacher Facing

### Student Facing

• Let’s add to teen numbers.

### Required Preparation

Activity 3:

• Gather materials from previous centers:
• Compare, Stage 1
• Number Puzzles, Stage 1
• Find the Pair, Stage 2

Building Towards

### Lesson Timeline

 Warm-up 10 min Activity 1 10 min Activity 2 10 min Activity 3 20 min Lesson Synthesis 10 min Cool-down 0 min

### Teacher Reflection Questions

What aspects of today’s lesson allowed each of your students to see themselves as productive mathematical reasoners?

### Print Formatted Materials

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