December 28, 2012

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.

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