# Lesson 4: More Practice with Addition

## Getting Started

### Questions to Explore

- How do we know when to add?
- What does it mean for numbers to be equal?
- How do we read and write in mathematical language?

### Facts and Definitions

**Commutative property of addition:**math law that states that the order of numbers does not matter when adding; also known as "turn-around facts"

### Skills

- Use addition and subtraction within 20 to solve word problems
- Apply properties of operations as strategies to add and subtract
- Add and subtract within 20, demonstrating fluency with addition and subtraction within 10
- Determine if equations involving addition and subtraction are true or false
- Understand the meaning of the equal sign

### Materials

- abacus (kit)
- apple slices
- crackers
- deck of playing cards (kit)
- fine point dry-erase marker (kit)
- pennies, nickels, and dimes
- play dollar bills (kit)
- small paper plates (kit)
- whiteboard (kit)

### Introduction

Materials: play dollar bills (kit)

Explain that you and your child have 10 dollars between you. Count out ten play one dollar bills so that your child can see that there are 10. Ask: "If we both have the same amount of dollar bills, how many do we each have?" Allow your child to count out the bills as needed. She should find that you both have five dollars. Next, ask: "What if you have two more dollars than I have? How much would we each have then?" Again, allow her to count out the bills as needed until she finds that she would have six dollars and you would have four dollars. Now, ask: "How many dollars will you have if I have only one dollar?" (nine dollars).