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What Are Number Bonds and Why Are They So Important?

If you are secretly wondering to yourself “Wait… what are number bonds?” every time you hear them mentioned, you are in the right place! After reading this blog post, you’ll know all about why and how you need to be using number bonds for subtraction and addition lessons.

When I first heard of them, I had no clue what they were. I remember staring at the little circles and lines and trying to figure out how I was supposed to use these number bonds in kindergarten math.  But I am willing to bet that after reading this blog post, number bonds are going to be your new favorite tool for helping young students understand basic math concepts! So if you want to stop wondering what are number bonds used for, read on!

What Are Number Bonds?

So let’s get right down to the first big question – really, what are number bonds?? I’m going to let you in on a little secret… number bonds are the ultimate visual representation for part-part-whole

what are number bonds

Basically, a number bond shows three numbers and two lines: two parts and the total when you add the parts together. The two lines connect the parts to the total. Sometimes, the appearance of number bonds varies a little, but that part-part-whole relationship is always there. 

Here are some pictures of number bonds you might see around:

number bonds
These are all variations of number bond drawings.

Number Bonds Addition 

So now that we’ve defined a number bond, it’s time for you to learn the secret power of using number bonds in your math lessons! 

The most basic use is to represent an addition problem. The numbers in each part represent the two addends. Then you add those together to get the number in the total.

Missing Total Problems

A number bond addition problem can be shown like this:

number bonds in kindergarten

The two addends go in the parts of the number bond and the sum goes in the total. This is a common way for students to practice adding. Filling in the total of a number bonds addition problem is the same as filling in the answer to a plus problem. 

Missing Addend Problems

But they can also be a helpful visual for a different kind of addition problem. 

missing addend example
Here is a number bonds example for a missing addend problem.

In this number bond addition problem, the total is given but there is one part missing. This provides a helpful visual for students to practice finding missing addends. This type of number bond is also helpful for remembering number pairs to make a certain sum. For example, having students practice with number bonds for 10 is a great way to learn those 10 pairs!

number bonds addition
These missing number bonds for 10 help students practice ways to make 10.

To see more number bonds in action, check out how I use them to help my students master their addition fact fluency!

Number Bonds Subtraction 

Okay, we’ve got number bonds addition down now. But can we also use number bonds for subtraction? You can absolutely practice subtraction with number bonds! In a subtraction problem, the first number is the total. The number you are taking away is one part. And the answer is the other part.

subtraction with number bonds
You can also use number bonds for subtraction understanding.

Using a number bond for subtraction can help students better understand the relationship between addition and subtraction. It helps to visualize subtraction as taking away one number pair from a sum to find the other pair.   

what is number bonds
Here is number bonds example relating addition and subtraction.

I always have students practice taking this type of number bond and writing a matching missing addend problem (we call this a mystery number problem!) as well as a subtraction problem. The more students understand the relationship between addition and subtraction, the stronger their math skills will become.

This is really the beauty of number bonds – they show so clearly how math is related. Finding number pairs, solving for a missing addend, and answering a subtraction problem are all actually the same thing! 

Number Bonds and Word Problems

When students learn to use number bonds in kindergarten, they can continue to use this part-part-whole visual for years and years! And they can more easily build on it as math gets harder. 

For example, most word problems are either asking you to find a missing total or a missing part. If students can learn how to put the facts from word problems into a number bond, then voila – it makes it so much easier to find the answer! I always teach my students to draw a number bond as their first step of solving a word problem.

Addition Word Problems

A number bond can be used to find basic addition problems where there’s a missing total. In this case, the word problem gives two parts that need to be added together. For example, “José received 5 marbles for his birthday and 4 for Christmas. How many does he have all together?” Students can fill in the number bond parts with the numbers given. This then gives them a clear visual to help them write the correct addition problem to find the answer.

number bonds example

Other times, a word problem provides information about the total and one part. For example, “There were 12 birds flying through the air. 7 were red, and the rest were blue. How many were blue?” For a problem like this, students must recognize that they are being given the total in the problem. Then they know to fill in the number bond with the total and one part. From there, they can solve the problem with a missing addend addition problem (I like to call these mystery number problems) or a subtraction problem.

word problem example

Subtraction Word Problems

In a subtraction problem, students are usually given a total and one part. This can take many forms, which can sometimes confuse students. For example:

  • “Jen had 14 baseball cards. She gave 6 away. How many does she have now?”
  • “Ahmed made 14 muffins. He ate some, and now there are 6 left. How many did he eat?”
  • “Penelope read 6 pages of her book today. If her book is 14 pages long, how many does she have left?”

These subtraction problems are all worded in different ways, with pieces of information in different orders. But they can be solved with the same number bond! I teach my students to recognize when they are being given a total and a part, so that they can fill in their number bond and identify the correct subtraction problem to find the answer.

subtraction example

Number Bonds Rock!

These are just some basic ways to use number bonds to teach foundational math skills to young students. I use them almost every day in math class, and they will continue to be an important part of my teaching.

How are you going to implement number bonds into your math teaching? Tell me in the comments!
xoxo
Laura

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20 Terrific Activities and Ideas for Teaching Number Bonds

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