Addition: 3-digit Numbers

Contributor: Erika Wargo. Lesson ID: 12213

In addition to adding one- and two-digit numbers, you will need to add three-digit numbers, like 365 days or video game scores! It's easy to practice with a card game, quiz, and problems you make up!


Arithmetic, Whole Numbers and Operations

learning style
personality style
Grade Level
Intermediate (3-5)
Lesson Type
Skill Sharpener

Lesson Plan - Get It!

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The amusement park gets a lot of visitors. Last weekend, 845 kids and 567 adults visited the amusement park. How many kids and adults visited in all?

When we need to combine two or more numbers, we add.

The numbers that are added together are called "addends." The answer to an addition problem is called the "sum." The order of numbers in addition does not matter, but usually we put the number with more digits first. When adding numbers, we add digits that have the same place value.

To add numbers, it can be helpful to follow these steps:

  1. Rewrite the problem vertically and line up the digits by place value spot and decimal point if there is one.
  2. Add the digits by column, starting with the "ones" column.
  3. Regroup if necessary. Remember that regrouping is necessary when ten "ones" get grouped as a ten, and are carried over to be counted with the other tens. You can also regroup other place value spots any time the number is ten or greater.

Now, you will learn how to find the sum of three-digit numbers.

845 + 567 =

  1. First, rewrite the problem vertically. Use grid paper to help you line up your numbers.
  2. Next, start adding in the ones column and don't forget to regroup! Move to the left and add the tens and hundreds.

The sum of 845 and 567 is 1,412:




















Discuss with a parent or teacher:

  • How do you know if you have to regroup?
  • Why is there is a one in the thousands place?
  • Share another strategy on how to add numbers. Can you add them horizontally or using a different way?

Now, it's your turn to practice adding three-digit numbers.

Check your understanding in the Got It? section.

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