How to Subtract the Common Core Way

It seems we have started back to school a good bit earlier than many of the rest of you, so I thought I might share our initial experiences teaching our first math unit after adopting the Common Core.  It may make it a bit easier to see the anchor charts we created.  I hope this proves helpful.

According to the Common Core, there is an emphasis on building number sense with third graders.  Our first unit has included Addition and Subtraction.  To build number sense, we have taught several strategies for addition and subtraction: using a hundreds chart, an open number line, place value blocks, and expanded form. 

Subtraction was the most challenging, especially for informing parents who want to help their children.  Not having text books written for common core makes homework a challenge.  In order to meed this need, we used a Math journal.  In that journal, we had students record an example homework problem that we did together in class.  Then we pasted small homework handouts (half sheets) underneath.  In a perfect world, this would have been just fine....but it's not a perfect world.  The problem we have run into is with those sweeties, that have trouble copying from the board or chart (for the homework example).  This copying thing is still a challenge for many 3rd graders.

I intend on letting my parents know they can check out this blog too, in order to see these anchor charts as well.

This anchor chart shows how to subtract using an open number line.  The hardest part for the students is using the skill of counting backwards, especially when going back over a ten-mark (ie 212, 201, 192).

(*I just realized I left off the letter "e" in the word "increase" below.  I'll fix it soon, upload a new photo and delete this comment, but I wanted to address it until I get the chance to make the change.)

 

 

  Here is my anchor chart for using place value blocks to subtract when there is no need to regroup. We started with real place value blocks.  Then we moved to the picture model.  After a bit of modeling, my kiddos really caught on to this strategy well. When subtracting without regrouping, this method tended to be especially easy for them.

 

However, when regrouping was needed, it got more complicated, but after a couple of days, my students found that they still preferred this strategy.  Here is the anchor chart to teach subtracting with place value blocks when regrouping was needed.

(technical difficulty with photo - will be corrected soon) 

 

If you have questions, I will be glad to try and answer them.