Today I am going to show you how to decomposing numbers in a step by step lesson that really worked for me! PLUS there’s a great little Jack-o-lantern teeth freebie to help you teach it, too! For this lesson, the children and I practiced decomposing the number four by putting teeth on Jack-o-lanterns! We just put some on the top of the mouth, and some on the bottom and then counted them.
It was great fun, and I think that the kids really GOT it! Obviously, you could do this with ANYTHING that has teeth- or anything that can easily be divided into two parts! So read on if you need to teach this skill! I have links to quite a few different freebies that I posted a while back that will also work to teach this skill. So look all they way at the bottom of the post for those!
Just in case you haven’t heard the term “decomposing number” before, that’s edu-speak that means “breaking down the number into it’s parts,” or “find all of the ways to make a given number.” For example, kids these days are supposed to know that four is the same as:
– Four and zero
– Three and one
– Two and two
– One and three
– Zero and four
So, there are five different combinations to make four. This is “pre-addition, and is supposed to lead to a deeper understanding of number sense in general. And YES- it’s in the Common Core in the “Operations and Algebraic Thinking” section for Kindergarten on up.
Can children as young as five years old learn this? YES!
MANY years ago, I worked with a dear Kindergarten teacher named Mrs. Kinne, (God rest her soul!), whose specialty was MATH. She insisted that kids needed to know this… and guess what? They ALL learned it! But that was about twenty years ago. And we didn’t call it decomposing numbers. We called it “Ways to Make ____.” LOL! (It was a little low tech, but it worked!)
When older children decompose numbers, they break larger numbers down into thousands, hundreds, tens, and ones. For example, children learn that 2,579 is the same as two thousands, five hundreds, seven tens, and nine ones. So what we are doing is the Kindergarten version of THAT!
The Math Machine
I decided to create a “Math Machine” to help us figure out how many teeth should go where. My little Math Machine is just a piece of dollar store jump rope with some small sections of TP rolls on the rope to slide and count. I put a couple of pool noodle pieces tied at the ends to secure the TP roll “rings” so that they wouldn’t fall off. This might work quite well on a dowel or piece of bamboo, as well, if you wanted it to remain stable or prop it up in front of the group of kids.
How to Teach Decomposing Number as a Guided Math Lesson:
– Show the children the Math Machine and have them count the rings (mine were cut from toilet paper rolls.)
– Push all four rings down to one end of the rope.
– Point out to the kids that when all of the rings are on one side, that means you have four rings on the left and zero on the right: Four and zero (or four plus zero = four.)
– Invite a child to push one ring to the right side of the rope.
– Ask: Are there still four? (You may be surprised that some may not know!)
– Point out: Three and one makes four. (Or, three plus one = four.) This is another way to make four. The first time we made four with four and zero, now we are making four with three and one.
– Invite a child to push another ring to the right side of the rope.
– Ask again: Are there still four? Can you count them? How did I make four now?
– Invite a child to push another ring to the right side of the rope.
– Ask: Are there still four? If so, how did I make four now? Are there always four, no matter where I put them?
– Invite a child to push the last ring to the right side of the rope.
– Discuss how many there are and what the rings mean now, etc.
After you introduce decomposing number to the group, then pass out your Jack-o-Lanterns and teeth (or whatever you are using to count with!)
You may need to do this on a different day if your students’ attention spans are “shot!”
Do this several times with different combinations of four (or whatever number you are making.)
The last step is to help them transfer what they know with manipulatives to the symbolic level on paper by having them draw the teeth!
I think it is easiest to start doing this with a dry erase marker first, because mistakes are very easily corrected.
Once the children get used to decomposing numbers with a dry erase marker, it should be more fun for them to do their own worksheets that they can keep and color.
Many young children will not be ready to begin writing equations. If so, they can just tell the teacher or a partner the number combinations that make four. Remember, children don’t have to write concepts down to understand them! Many young children have much, much more going on in their brains than they are able to express with a pencil!
You can download this fun freebie here! I hope you enjoy it, and if you have any ideas on how to teach this concept in a better way (or even just a different way, I would love to know your thoughts!
As you move forward with addition, you may want to teach this Addition Song below. My kids loved it!
And by the way, if you like this, you may also like these great freebies as well:
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