Addition and Subtraction

Introduction to Addition

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#### Lesson 1: Introduction to Addition

### What is addition?

#### Try This!

### Writing Expressions

#### Try This!

### Solving Problems

#### Try This!

#### Ways to Count

### Practice!

#### Set 1

#### Set 2

#### Set 3

#### Set 4

#### Set 5

**Addition** is a way to put things together. When you **add** two amounts, you're counting them together, as one larger amount. Addition happens all the time in real life.

What if there were** four more** rabbits?

As you can see, if you have **4** rabbits and add **4 **more, you'll have **8 **rabbits in total. You could write it like this:

4 + 4 = 8

4 + 4 = 8 is a **mathematical equation**. You could read it like this: Four plus four equals eight. A mathematical equation is basically a **math sentence**. It uses numbers and **symbols** instead of words. When we write out equations with addition, we use two symbols: **+** and** =**.

The **plus sign** (**+**) means two things are being added together. This is why we put it between the rabbits—we had 4 rabbits and added 4 more.

The other symbol in our equation is the **equals** **sign** (**=**). When you see the equals sign in an equation, it means two are more things are **equal**, or **equivalent**. Things that are equivalent don't always look or seem exactly alike, but they mean the same thing.

For instance, when you see someone you know, there's a few things you might say:

These words aren't exactly alike, but they mean the same thing. They're all ways to greet someone.

In math, the equals sign shows that two numbers or expressions **mean the same thing**, even though they might look different. Remember our rabbits? Because there were 8 rabbits total, we wrote 8 to the right of the equals sign.

See how each side means 8? There are 8 rabbits on the left, and the number 8 on the right. Both sides are **equal**.

Fill in the blanks to complete the equations.

On the last page, we looked at some mathematical expressions. Expressions are useful, since they can help you keep track of the amounts you're adding.

**Any addition problem can be turned into a written expression.** For instance, say that you planned to have three friends come over for dinner. At the last minute, you invite two more. To get the total number of friends who are coming to your house, you might write an expression like this:

3 + 2

The expression is just another way of describing the situation: **three** friends plus **two** more are coming over for dinner.

Write these situations as mathematical expressions. Don't solve the problems yet — simply set them up.

You ate **three** pieces of pizza for lunch. At dinner, you ate **two** more:

You already waited **five** minutes to see the doctor. The nurse tells you to wait **five** more minutes:

Your coat has **four** buttons on the right side and **three** buttons on the left side:

Now that you know how to write addition problems, let's solve some. When you're just getting started, you might find it easier to use **counting **to solve problems.

For instance, can you use counting to write and solve this problem?

With that problem, you were able to count the objects you were adding. In real life, some people like to count with their fingers. Other people use small objects, like buttons or pennies. Others might make small marks on a piece of paper. When you're learning to add, it's OK to count! The more you practice, the easier it will get to add without counting.

Let's look at two ways to solve addition problems with counting. First, we'll count with **objects**.

Another way to solve addition problems is to use a **number line**.

Practice adding these problems. There are **5** sets of problems, with **3 **problems in each set.

6 + 1 =

2 + 0 =

5 + 3 =

4 + 5 =

3 + 1 =

2 + 2 =

1 + 8 =

0 + 3 =

7 + 6 =

4 + 8 =

9 + 1 =

7 + 5 =

5 + 5 =

3 + 2 =

6 + 8 =

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