Related Addition Facts

Overview

By joining two groups together, you can decide how many there are in all.

When we add two numbers, we learn and write a math fact.

Like this:

Let’s take a look at the example above.

There are 2 circles in the first group and 1 circle in the second group.
We can ADD them by joining the two amounts together.

This will give us the total number of circles.

When we ADD 2 plus 1, we have 3 in all.
We say: TWO plus ONE equals THREE.
We write it like this: 2 + 1 = 3

We can also use these same three numbers in our math fact: 2, 1, and 3 to make a RELATED FACT.

This time our math fact will read: 1 + 2 = 3 because we added 1 and then 2 to get a total of 3.

2 + 1 = 3 is related to 1 + 2 = 3

They include the same three numbers.

Let’s take a look at another example with numbers.
This time, we are joining the numbers 4 and 5.

These numbers are known as ADDENDS.

Recall from our earlier lessons, that addends are the amounts that will be joined together.

This problem reads as 4 + 5 = 9.
When the ADDEND 4 is joined with the ADDEND 5, we get a SUM of 9.

Again, we have two groups and we are joining them together.

These facts are related:

4 + 5 = 9

5 + 4 = 9

Related addition facts always have the same sum, or answer.

Let’s take a look at these facts.

5 + 1 = 

1 + 5 = 

They are related and have the same addends. We can join them to find the sum.

5 + 1 = 6 and 1 + 5 = 6

Here is another example:

2 + 8 =

8 + 2 =

They are related and have the same addends. We can join them to find the sum.

2 + 8 = 10 and 8 + 2 = 10

Sometimes, you might come across an addition fact with a missing addend. You can use related facts to help you solve. Let’s take a look at this pair of facts:

3 + 4 = __

4 + __ = 7

In the first math fact, our sum is missing. We can add 3 and 4 to get an answer of 7.
Our second fact is related. It will have the same three numbers as our first fact.
Therefore,

4 + 3 = 7

Here is another example:

2 + 9 = __
9 + __ = 11

In the first math fact, our sum is missing. We can add 2 and 9 to get an answer of 11.
Our second fact is related. It will have the same three numbers as our first fact.

Therefore,

9 + 2 = 11

Now that you have a much better understanding of related addition facts, let’s go ahead and quickly review key words that relate to addition in the chart below.

Knowing these keywords will help you understand that in order to solve the problem, you must add.

We can also write related addition facts when we are given three numbers. Let’s look at this example:

5   8   3

We know that the sum in each addition fact must be the largest number. Which number is the largest: 5, 8, or 3?

The number 8 is the largest. Therefore, the other two numbers will be our addends.

__ + __ = 8

__ + __ = 8

Let’s create our related facts using the numbers 5, 8, and 3!

3 + 5 = 8

5 + 3 = 8

Let’s look at one more example:

13   7   6

We know that the sum in each addition fact must be the largest number. Which number is the largest: 13, 7, or 6?

The number 13 is the largest. Therefore, the other two numbers will be our addends.

__ + __ = 13

__ + __ = 13

Let’s create our related facts using the numbers 5, 8, and 3!

7 + 6 = 13

6 + 7 = 13

Practice Question 1

Let’s practice! Write the addition sentence and related addition fact and solve the problem below.

REVEAL THE ANSWER

Practice Question 2

Let’s try another! Write the addition sentence and related addition fact and solve the problem below.

REVEAL THE ANSWER

Practice Question 3

Take a look at the math sentence below. Write the related addition fact. Then solve.

7 + 8 = 

REVEAL THE ANSWER

Practice Question 4

Take a look at the math sentence below. Write the related addition fact. Then solve.

10 + 4 = 

REVEAL THE ANSWER

Practice Question 5

Look at the groups below.
How many are there in all?
Write the related addition sentences and solve.

REVEAL THE ANSWER