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1.1: Whole Number Addition

Difficulty Level: At Grade Created by: CK-12
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Have you ever been to the zoo? Have you ever had to add whole numbers to solve a problem? Adding whole numbers is a skill that can help you to solve many real - world problems. Jonah is a student volunteer at the city zoo. He is working with the seals. Jonah loves his job, especially because he gets to help feed the seals who live at the zoo. There are 25 female and 18 male seals. In order to figure out how much to feed them, he will need to know the total number of seals. Use what you will learn in this Concept to help Jonah figure out the total number of seals.


Adding whole numbers is probably very familiar to you; you have been adding whole numbers almost as long as you have been in school. Here is a problem that will look familiar.

\begin{align*}4 + 5 = \underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}4+5=

In this problem, we are adding four and five. We have four whole things plus five whole things and we get an answer of nine. The numbers that we are adding are called addends. The answer to an addition problem is the sum. This first problem was written horizontally or across.

In the past, you may have seen them written vertically or up and down. Now that you are in the sixth grade, you will need to write your problems vertically on your own.

How do we do this?

We can add whole numbers by writing them vertically according to place value. Do you remember place value? Place value is when you write each number according to the value that it has.

Millions Hundred Thousands Ten Thousands Thousands Hundreds Tens Ones
1 4 5 3 2 2 1

This number is 1,453,221. If we used words, we would say it is one million, four hundred and fifty-three thousand, two hundred and twenty-one.

What does this have to do with adding whole numbers?

Well, when you add whole numbers, it can be less confusing to write them vertically according to place value. Think about the example we had earlier.


If we wrote that vertically, we would line up the numbers. They both belong in the ones column.

\begin{align*}& \quad 4\\ & \ \underline{+5}\\ & \quad 9\end{align*}4 +59

What happens when we have more digits?

\begin{align*}456 + 27 = \underline{\;\;\;\;\;\;\;\;}\end{align*}456+27=

When you have more digits, you can write the problem vertically by lining up each digit according to place value.

\begin{align*}& \quad 456\\ & \ \underline{+ \ 27}\end{align*}456 + 27

Now we can add the columns.

Now let's practice.

Example A

\begin{align*}3,456 + 87 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}3,456+87=

Solution: 3,543

Example B

\begin{align*}56, 321 + 7, 600 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}56,321+7,600=

Solution: 216,091

Example C

\begin{align*}203,890 + 12, 201 = \underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}203,890+12,201=

Solution: 63,921

Now let's go back to Jonah and the seals. Jonah knows how many male seals and how many female seals are in the seal area at the zoo. He wants to figure out how many seals there are altogether. To accomplish this task, Jonah will simply need to add the two quantities together.

Here is what he knows:

25 females 18 males

Now we add those values together.

\begin{align*}25 + 18 = 43\end{align*}25+18=43

There are 43 seals at the zoo.


Here are the vocabulary words found in this Concept.

the numbers being added
the answer to an addition problem
up and down

Guided Practice

Now here is one for you to try on your own. Add the following pair of whole numbers. Then you can find the answer below.

\begin{align*}675 + 587 = \underline{\;\;\;\;\;\;\;\;}\end{align*}675+587=


To solve this problem, we line up the columns vertically according to place value.

When you have more digits, you can write the problem vertically by lining up each digit according to place value.

\begin{align*}& \quad 675\\ & \ \underline{+ 587}\end{align*}675 +587

Now we can add the columns.

Our answer is 1,262.

Interactive Practice


Video Review

These videos will help you with adding whole numbers.

Khan Academy Basic Addition


Directions: Use what you have learned to solve each problem.

1. \begin{align*}56 + 123 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}56+123=

2. \begin{align*}341 + 12 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}341+12=

3. \begin{align*}673 + 127 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}673+127=

4. \begin{align*}549 + 27 =\underline{\;\;\;\;\;\;\;\;\;}\end{align*}549+27=

5. \begin{align*}87 + 95 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}87+95=

6. \begin{align*}124 + 967 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}124+967=

7. \begin{align*}1256 + 987 =\underline{\;\;\;\;\;\;\;\;\;}\end{align*}1256+987=

8. \begin{align*}2345 + 1278 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}2345+1278=

9. \begin{align*}3100 + 5472 = \underline{\;\;\;\;\;\;\;\;\;}\end{align*}3100+5472=

10. \begin{align*}3027 + 5471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}3027+5471=

11. \begin{align*}13027 + 7471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}13027+7471=

12. \begin{align*}23147 + 5001 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}23147+5001=

13. \begin{align*}23128 + 7771 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}23128+7771=

14. \begin{align*}43237 + 5071 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}43237+5071=

15. \begin{align*}22027 + 6001 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}22027+6001=

16. \begin{align*}45627 + 2471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}45627+2471=

17. \begin{align*}83027 + 51471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}83027+51471=

18. \begin{align*}94127 + 5471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}94127+5471=

19. \begin{align*}83777 + 3321 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}83777+3321=

20. \begin{align*}95527 + 12471 =\underline{\;\;\;\;\;\;\;\;\;\;}\end{align*}95527+12471=

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An addend is the number being added in an addition problem.


Horizontally means written across in rows.


The sum is the result after two or more amounts have been added together.


Vertically means written up and down in columns.

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Difficulty Level:
At Grade
Date Created:
Oct 29, 2012
Last Modified:
Sep 12, 2016
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