1.OA.2: Adding Three Numbers

I can solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20.

What Your Child Needs to Know

This standard focuses on helping your child add three numbers together to solve word problems. Students need to understand that they can add the numbers in any order (commutative property) and group them in different ways (associative property) to make the addition easier.

This skill builds on your child's ability to add two numbers and extends their understanding to more complex problems. Being able to add three numbers efficiently will help your child develop mental math strategies and prepare them for multi-step problems in later grades.

Real World Practice

Visual models and hands-on activities

Visual Models

1. Number Bonds

Number bonds show how numbers can be broken apart or combined. For adding three numbers, you can create a two-step number bond:

Example: 4 + 5 + 6

First combine 4 + 6 = 10, then add 10 + 5 = 15

2. Number Line

Start at the first number, then jump forward by the second number, then jump forward again by the third number.

Example: 3 + 7 + 2

Start at 3, jump forward 7 spaces to 10, then jump forward 2 more spaces to 12.

3. Ten-Frame

Use ten-frames to organize numbers and see how they combine to make 10.

Example: 8 + 5 + 2

Fill 8 spaces on the first ten-frame, then add 2 more to complete the ten. You now have 10 + 3 = 13.

4. Part-Part-Whole Model

Use a part-part-part-whole model with three parts connecting to one whole.

Example: 4 + 3 + 6

The three parts (4, 3, and 6) combine to make the whole (13).

Everyday Activities

1. Grocery Math

When shopping, ask your child to add the number of fruits or vegetables you're buying:

"We have 4 apples, 3 oranges, and 6 bananas. How many pieces of fruit do we have altogether?"

2. Cooking Counts

While cooking, have your child help count ingredients:

"We need 5 strawberries, 7 blueberries, and 3 raspberries for this recipe. How many berries in total?"

3. Score Keeper

During family game night, have your child keep track of scores by adding three rounds together.

4. Daily Collection Count

If your child collects items (rocks, stickers, toy cars), have them count three different groups and find the total.

5. Three-Part Stories

Create three-part stories that involve addition:

"You saw 4 birds at the park, then 5 more birds flew in, and then 2 more joined them. How many birds were there in all?"

Quick Checks

Strategies and quick activities

Strategies When Your Child Struggles

1. Look for Friendly Numbers

Teach your child to look for combinations that make 10 or doubles they know.

Example: 5 + 6 + 5

Rearrange to 5 + 5 + 6 = 10 + 6 = 16

2. Use Manipulatives

Use physical objects like counters, blocks, or beans to represent each number, then count all objects.

3. Draw Pictures

Have your child draw simple pictures to represent each number in the problem, then count all items.

4. Break It Down

Help your child break the problem into two steps: first add two numbers, then add the third number to that sum.

5. Practice Doubles

Practice doubles facts (1+1, 2+2, etc.) so your child can quickly identify when two of the three numbers make a double.

5-Minute Practice Activities

Activity 1: Roll and Add

Roll three dice and add the numbers together. For an easier version, use dice with only 1-3 on them.

Activity 2: Card Addition

Remove face cards from a deck, then draw three cards and add their values. Aces count as 1.

Activity 3: Three-Number Flash Cards

Create flash cards with three single-digit numbers to add. Start with smaller numbers and gradually increase.

Activity 4: Story Problems

Create simple word problems using your child's interests:

"You have 3 red cars, 5 blue cars, and 2 green cars. How many cars do you have altogether?"

Activity 5: Number Hunt

Find three numbers in your environment (on food packages, license plates, etc.) and add them together.

Check Progress

Track improvement

By the middle of the year, your child should:

  • Add three single-digit numbers with sums up to 10
  • Identify combinations that make adding three numbers easier (like making 10)
  • Solve simple word problems involving three addends

By the end of the year, your child should:

  • Add three numbers with sums up to 20 fluently
  • Apply the commutative and associative properties to make addition easier
  • Group numbers strategically when adding three numbers
  • Solve word problems with three addends in various contexts

Mastery Signs

Your child understands this concept when they can:

  • Add three numbers accurately and efficiently
  • Rearrange numbers to make addition easier (like finding pairs that make 10)
  • Explain their strategy for adding three numbers
  • Create their own word problems involving three addends
  • Apply this skill to solve real-world problems

Differentiation

Support for all learning levels

Below Grade Level

Practice problems focusing on adding three numbers with sums less than 10, with visual supports.

Download Practice Worksheet

At Grade Level

Standard practice with adding three numbers with sums up to 20, including word problems.

Download Grade Level Worksheet

Above Grade Level

Challenging problems that include adding three numbers in various contexts and creating their own word problems.

Download Challenge Worksheet