# Lesson 13

More Story Problems with Teen Numbers

### Lesson Purpose

The purpose of this lesson is for students to solve Take From, Result or Change Unknown story problems.

### Lesson Narrative

In previous lessons, students added and subtracted within 20 with teen numbers that did not require composing or decomposing a ten. They used counting on, take away, the $$10 + n$$ structure of teen numbers, and the relationship between subtraction and addition.

The purpose of this lesson is for students to solve a new type of story problem—Take From, Change Unknown. Students also solve a familiar problem type—Take From, Result Unknown. They use methods that make sense to them and then make connections between methods.

• Action and Expression
• MLR2

Activity 1: Sitting or Standing

### Learning Goals

Teacher Facing

• Solve Take From, Result or Change Unknown story problems.

### Student Facing

• Let’s solve story problems.

### Required Preparation

Activity 3:

• Gather materials from previous centers:
• Shake and Spill, Stages 3-5
• Compare, Stage 1
• Number Puzzles, Stage 1

### Lesson Timeline

 Warm-up 10 min Activity 1 15 min Activity 2 10 min Activity 3 15 min Lesson Synthesis 10 min Cool-down 0 min

### Teacher Reflection Questions

Think about who volunteered to share their thinking with the class today. Are the same students always volunteering, while some students never offer to share? What can you do to help the class understand the value of hearing the ideas of every mathematician?

### Print Formatted Materials

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