# Lesson 18

### Lesson Purpose

The purpose of this lesson is for students to find expressions equivalent to $$10 + n$$ expressions. Students then look for patterns in the expressions.

### Lesson Narrative

In the previous lesson, students discussed how making a ten can help them find the value of expressions in which one addend is close to 10. In this lesson, students continue to add two addends within 20, focusing on how making a ten can help them add. In the first activity, students match addition expressions to their equivalent $$10 + n$$ expression. In the second activity, students participate in a Gallery Walk, noticing patterns between expressions that represent a sum. In each activity, students have access to double 10-frames and two-color counters as they explore patterns they notice.

• Action and Expression
• MLR7

### Learning Goals

Teacher Facing

• Look for and use patterns in addition expressions to add within 20.
• Make a ten to find the sum of two numbers within 20.

### Student Facing

• Let’s look for and use patterns to help us add within 20.

### Required Materials

Materials to Gather

Materials to Copy

• Compare Stage 2 Addition Cards to 20

### Required Preparation

Activity 1:

• Create a set of Compare Stage 2 Addition Cards to 20 from the blackline master for each group of 3.

Activity 3:

• Gather materials from previous centers:
• Shake and Spill, Stages 3–5
• Compare, Stage 1
• Number Puzzles, Stages 1 and 2

### Lesson Timeline

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

### Teacher Reflection Questions

As students worked in their small groups today, whose ideas were heard, valued, and accepted? How can you adjust the group structure tomorrow to ensure each student’s ideas are a part of the collective learning?