Addition v. Subtraction

A couple of weeks ago, the little guys and I started discussing strategies to solve subtraction story problems (see post).

Just as the kiddos were getting comfortable with this idea, I threw in a new twist ... addition and subtraction word problems on the same page!  In order to solve these problems, the kiddos had to determine if the problem required addition or subtraction.  For this, I really focused on visualizing and retelling the action of the story.  We also noticed that word problems often have key words that suggest either addition or subtraction. 

I knew that taking this next step would be challenging, and although I tried to make it seem like a very exciting step, some of the kiddos were still a litte wary.  In order to make things as easy as possible, I wanted to create an anchor chart that contained tips and strategies the little guys could reference as they went about tackling these problem sets.  

Here is what I came up with:

So far it has proved very helpful!  When a kiddo comes to a problem that he is not sure what to do with, I encourage him to check the chart for key words and then choose a relevant strategy.  As one of my adorable kiddos put it, pointing to the chart, "This really helps me!" As a  class, they are getting better at deciding which operation to use and choosing logical strategies.  

{from Investigations Math, 1st Grade}

Some of the kiddos have even moved on to "challenging word problems" which take a little more thought and use slightly larger numbers. They continue to reference the chart thoughtfully and are beginning to internalize the strategies that work best for them. I love math anchor charts!  

Subtraction

We have reached a milestone in first grade... starting subtraction!  Subtraction is a big deal in first grade.  The kiddos know it exists and they get the general concept, but it still seems like a bit of enigma.  Last week we finally figured it out!

Our Investigations Math curriculum has a lot of games that introduce and reinforce concepts, so we started by adapting some familiar math games from addition games to subtraction games.  The kiddos practiced counting back and using doubles and familiar number combinations to find the difference between two numbers.  Most of the kiddos were able to do this pretty easily out loud and on their fingers.

Then I introduced subtraction story problems.  The most challenging thing about subtraction seems to be remembering which strategies to use to solve a subtraction problem.  A lot of kiddos are so comfortable using addition strategies that they get themselves all confused by drawing the wrong picture or trying to count all instead of counting back.  Therefore, I spent a lot of time this past week retelling the sequence of events in subtraction story problems and modeling what happens when we subtract.  We used counters, fingers, and pictures.  Then we created an anchor chart to remind us of the subtraction strategies we know.

The kiddos have been doing a pretty good job of incorporating these strategies into their mathematical repertoire.