Thursday, May 09, 2013

composing & decomposing {CC K.NBT.1}

Composing & decomposing numbers.  This is a term I had to keep going back to because as I was looking for new strategies and ways to teach it I was like..."Wait.  What does that even mean?!"  :)  Basically, composing and decomposing is an intro to place value and helping students see that a "10" is really made up of a group of ones.

Here are a few things that have worked for us.  Starting with...s-l-o-w it down.  This is a concept that takes their brains in a new direction of thinking so let your math centers hibernate for a week or so and focus on some good, whole group instruction and practice time.

{Sing it}
Harry Kindergarten has done it again.  He's revamped his Numbers in the Teens song to get the kids singing about groups of tens and extra ones.  I started introducing this during our math brain break time a couple of weeks in advance just to get them familiar with it.

Then we moved into "acting it out" while we sang along.  Each kid built a 10 tower using pop cubes of the same color.  All of the other pop cubes were spread out in the middle of the carpet.  As we sang along, I paused the video at each number so the kids could grab another "one" and double check their groups.  I told them the color of their ones didn't matter because I wanted the difference between the group of 10 and the single ones to be clear.

We repeated this to start the lesson for the next few days and as they got more familiar with adding a one, I didn't have to pause the song anymore.

{build it}
Next, I grabbed a dry erase board and wrote a random number from 11-19 to see if they could still build it when the numbers didn't go in order.  We practiced this for a few days as part of the lesson.  Then, to flip flop their thinking, I built a number using pop cubes and let the kids all have dry erase boards.  This was a little harder because some of them wanted to count all of my cubes instead of seeing the 10 tower as a known group.  {This was also a great teaching moment to explain WHY it matters how they write the numbers - if they wrote 15 as 51, I'd build 51 to show the difference.}

Again...practice for a few days.  :)

Once I was ready to introduce practice centers, this was an easy activity I knew they could do on their own.  The kids took turns writing a teen number while their friends built it.  {you can see our pre-built single colored 10 towers & multi-colored ones in this picture.}  They passed the dry erase board around so they could each practice being the teacher.

{draw it}
This could be done in a center but I used it as my last whole-group activity to get a better grasp of who was understanding the concept.  We did 11 and 12 together as I modeled how to draw on the board.  Then they finished the rest on their own.  {This folding didn't allow us to draw 19 but I figure if they could do 13-18, that was a pretty accurate measure.}  ;)

{add it}
We learned this game in partners and then they practiced on their own when it was time to rotate centers.  The first 10s frame is already built to keep that group intact.  My kids drew a number card, added that many counters to the second 10s frame and wrote the number sentence.  I also had them explain their board to their partner before erasing - "14 is a group of 10 plus 4 ones."

{practice it}
This week, in addition to our current review centers, I'm going to introduce this {free} matching activity from Clearly Kindergarten... well as some of the fabulous games and practice centers from my friend Leslie at KindergartenWorks!

Hang in there.  They will get it!!  :)  And remember to enter for your chance to win an Origami Owl locket:
{winner chosen on Sunday at 5pm Eastern time}


  1. This is such a fabulous post Kristin! I pinned it so I could reread it next year at the beginning of the year with my first graders. Thanks!
    Sarah's First Grade Snippets

  2. I love the song! I use it often with K-1 students ... just something I noticed... you talk about what composing and decomposing numbers means. Yes, you can compose and decompose numbers using place value; and in this standard that is how we want kids to compose and decompose the teen numbers. But in the common core, the terms mean to be able to put together and break apart ANY numbers ...this does not have to be done using place value properties...for example, a student might subitize a pile of counters by seeing 5 and 3 and saying that is 8...they composed 8 from 5 and 3... we play a game called cover up or how many am I hiding to get students to decompose numbers... I show that I have 8 chips ...I cover some (3) and show 5 and ask how many am I hiding. The students have to decompose 8 into 5 and some more . This skill is a crucial foundational skill for developing number sense that they will continue to expand and use as they get older. Being able to break apart numbers easily .... for example a second or third grader given the problem 153 +38 might decompose the 38 into 7 and 31 because 7 more makes the next 10 (160) and adding on 31 is easy...or they may decompose it further using place value properties into 30 and 1 and then adding on the tens and ones separately. Or as a 4th grader multiplying 24 X 14 I might decompose the 14 to 10 and 4 and do (24X10) and then add on (24X4)...

  3. Where did you get the decomposing mat? Did you make it? Do you have a digital copy that I could have? Thanks for a great post. I am going to use your ideas with my kiddos next week!


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