Decomposing Numbers – Part 1


Decomposing numbers means to break down numbers into their sub-parts. Common Core standards has kindergarten students decomposing numbers in two ways. The first is to decompose numbers into their tens and ones (focus on numbers 11-19) and the second is to show how any number 1-10 can be created using a variety of addends. I want to focus with you on the NBT.1 Common Core standard which addresses the tens and ones (or place value) aspect of breaking and creating numbers.

Let’s look at how it develops and how we can practice and extend it for our kinders. I’ve got three posts in this series for you!

Decomposing Numbers - KindergartenWorks

Part 1 – Understanding Decomposing/Composing Numbers as Teachers

There are two main pieces of this standard:

  • The first is using objects and words to show that teen numbers have a group of ten and some ones.
  • The second is expressing this break down using equations.

Why Do We Expect Them to Decompose and Compose Numbers?

{And why do I keep writing about it?}

The simple answer is because there is value in students being able to see the groupings, relationships and patterns in numbers. We are laying the foundation for students to be able to do 53+12 and see that they can manipulate it into making 50+15 or 60+5 or 50+10+3+2 or any other variety of ways to see the quantity as it makes sense to them.

Decomposing Numbers - KindergartenWorks

Now that’s the bigger picture and carries us into older grade level Common Core standards… so lets bring it back down to our kindergarten level and working with slightly accelerated students. We are working on understanding that numbers 11-19 have a group of ten and then ones. Students in kindergarten are often excited about bigger numbers and want to explore what those other numbers are, look like and “how big” they are.

Decomposing Numbers - KindergartenWorks

Seeing numbers broken down into a pattern of their groupings of tens and then the addition of some ones makes numbers palatable and simple. It gives a “visual” {especially if you are representing with ten frames} to what 6, 16 or 67 really looks like and is.

Decomposing Numbers - KindergartenWorks

Visualizing Groupings With Accelerated Students

If you have students with good number sense within 100, then you can deepen their skills by playing games like subtract 10 bump. This roll and cover bump game is perfect for visualizing the groups of ten in a given number and then visualizing one group less. Have a 100’s chart handy or some pre-filled ten frame cards as a tool if needed, but my goal is to work on visualizing with these kinders.

Hit or Miss - Subtract 10 Bump (Roll and Cover) Game

Hit or Miss Subtract 10 Bump

To play this game, students roll two dice to create a number (11-66). They subtract 10 and then cover that space on the two-page game board. It follows the typical “bump” rules to where players can bump or lock their space. First pirate, I mean player, to lay out all of their cannons (linking cubes) wins.

Decomposing Numbers - KindergartenWorks

Next Post in this Series:

I hope you can use some of these ideas to better understand decomposing numbers. What’s your experience with this standard? If you like what I do here on KindergartenWorks, then be sure to subscribe today. I look forward to sharing ideas with you weekly.

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