math, Number Strings

Minus/Subtraction/Take-Away

Minus…subtraction…take-away.  Do these all mean the same thing?  They are certainly all represented by the same symbol.

Last week the math coordinator was in  my class for a few days.  (Here name is Melissa and she blogs here!)  After watching me do a number string related to subtraction, she encouraged me to always say “subtract” when I am reading the problem to the class, rather than “take-away.”  Some kids will actually do some adding to solve these types of problems, and by always saying “take-away” I would be restricting their thinking and maybe even imply that they need to use a certain strategy, namely that they need to remove.

I know that there are different ways to solve a subtraction problem:  add on, count back, think of it as a part of a fact family and figure out the addition problem.  But I hadn’t really been intentional about my language when discussing subtraction with the class.  I was more focused on the answer!  (I’m hanging my head in shame!) (not really…but you know what I mean!)

On Thursday and Friday we had bus cancellations, so I didn’t really get a chance to try this out until today.  We were working a Number String from Cathy Fosnot’s mini-lesson book.  We talked about 14+1, then 14-1 (Did you read that 14 subtract 1? or 14 minus 1?)   Then I gave them 14-13.  You can’t see them in this picture, but I had the maths.ca relational rods going in the background, and had build 14+1, and 14-1, and those were still visible to the students. I saw lots of kids with their fingers out counting back.  It’s an okay way to get  correct answer, but very inefficient.  However, I then asked my favourite student (my daughter!!)  to tell me how she solved it.  I’d seen her working away on those fingers, and I know that if she spent a tiny bit of time thinking before she started that, the answer would have been obvious to her.  Knowing this, I had to ask her about her strategy.  “Well, I thought about having 14 cookies, and then I ate 13 of them, so yeah…one is left.”  This is not totally unreasonable for her (don’t judge my parenting!) especially if they are Viva Puffs!   I annotated her thinking like this:

I pointed out to everyone that CC was thinking of subtraction as “taking away” something.  And then asked others what they thought about when they saw a subtraction sign.  Someone else said, “Well, I knew you would only need one more to get from 13 to 14, so I knew it would be 1.”  I talked about how that child was thinking about the difference between 14 and 13, which was different from CC’s but they both still got the same answer.  Then we did 2 more problems from the string, and talked about the “take-away” strategy and the “find the difference” strategy.

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Someone even mentioned that they thought about 9+2=11, which is a great connection to some work we did a week or so ago, so that was awesome too.

It’s funny how being intentional about how I was reading that symbol to the class changed the strategies they used.  This wasn’t truly the goal of the Number String, but “m delighted by the results.  I am hoping the forecasted 25-35 cm of snow (and 80 Km/h winds!) hold off until late on Tuesday so we can work on this again tomorrow.  I feel like we are developing a really big understanding about subtraction!

math, Number Talks

Collaboration

We’ve taken a little break from partner work in our class.  Increasingly our struggles with problem solving were getting all tangled up.  Instead of feeling frustrated because working with partners is hard, I felt too many of the students were starting to blame math for the problem and I didn’t want that feeling to perpetuate.  We took some time to do some worksheets *GASP* alone – mostly because I needed a bit more data to feel confident about assigning letter grades on report cards.  Geometry has been the focus of these.  We also took some time to loop back to patterning because this seems to be an area where lots of people hadn’t made a connection between patterning and using an open number line to add numbers.  I think we are there now!

Before we dive into our next unit (Trades, Jumps and Stops from the Context for Learning kits by Cathy Fosnot), I’m going to take some time next week to do some work on the collaboration part.  I have been assigning partners all year.  We’ve talked a lot about why I am choosing those particular partners for everyone.  Now it is time for them to make some choices of their own and I will also be asking them to justify those choices and articulate what makes a good partners.

Once partnerships are established, partnerships last for a month.  They stick together for every part of our day when they might need a partner – writing, reading, science, math and anything else. We will be working on building our collaboration skills all day long.  Specifically in math, I am going to ask everyone to do a “turn and talk” with their partner during each Number Talk.  Usually we do what I think most people do:  I put up a problem, kids work them out alone, then we discuss them together.  I think the turn and talk time will help them practice actually talking to their partner about how to solve the problems.  They will be empty handed, so they can focus on talking about the math instead of arguing about who will be using the marker to write it down.

The second thing I am going to do is create some problems for everyone to solve.  Today we are going to do an activity from The Super Source where partners work together on some describing and listening skills.  One builds a design using no more than pattern blocks. The second partner is not allowed to see this.  The first partner describes the design that was built so the second partner can recreate it.  It’s a tricky exercise for 7 year olds, believe it or not.  Positional language,  attributes of geometric shapes, and expanding on one’s own words are all practiced.  I find that the person describing often reverts to giving directions such as “get a triangle and put it on top of the square…no that way…no that way…no down…YES!”    The other problems are going to involve some addition, maybe some subtraction and will be put in a context they can work with.

The final thing I really need to work on is how to respectfully disagree, and how to accept that “No, I don’t think so” isn’t the same as “I hate your guts and will never speak to you again!”  It’s a hard one, but necessary.

I had initially planned for next week to be the start of my next unit.  But I’m feeling better about this plan of action.  It’s going to help us have a smoother run through the unit, and it is going too help me set up the Math Workshop groups we’ll need during the unit.