Lesson 3 Relate Addition and Subtraction within 20

    • Let’s find the number that makes equations with 20 true.

Warm-up Number Talk: Addition and Subtraction

Find the value of each expression mentally.

Activity 1 Introduce What’s Behind My Back, 20 Cubes

We are going to play What’s Behind My Back, this time with 20 cubes.

Activity 2 Make the Equation True

Find the number that makes each equation true. 

  1. If you have time:  

Practice Problem

Problem 1

Find the number that makes each equation true. Show your thinking using drawings, numbers, or words.