8+9: four strategies for counting and adding

8+9: four strategies for counting and adding

Yesterday was our first mental math as a 3rd grade summer school class. This mental math number talk was designed to be a ‘warm up’ to the instructional routine; in terms of the standards, this problem would be well suited for late first grade. However, I wanted a problem that would be slightly easier than the 3rd grade standards, so that the students could focus on developing productive norms for number talks.

I started by discussing with the students what a number talk was, what mental math was, and what their jobs would be: to think about the problem and multiple ways of solving it, to talk at a conversation level to their partner and listen to their strategies, and to be ready to share with the class AND listen to their peers’ ideas during whole-group discussion.

We rehearsed these norms and actions several times, first with questions designed only to get them used to holding their ideas privately until asked to share with a neighbor: “Think of as many animals as you can that are green” and then “Think of something you have exactly 3 of in your house.” Students are generally pretty eager to share responses to these kinds of questions, so they are helpful for giving them a chance to practice holding their ideas private until asked to talk to a partner or share with the class.

We then did one more ‘practice round’ with the problem 2+2 to again reinforce, review, and label productive student actions, like showing on their fist with fingers how many strategies they had, holding their ideas privately until asked, then sharing at a low conversation level with a partner once asked.

When it was finally time to do the ‘real’ problem for the day (8+9), these norms were pretty firmly in place. I had a few kids whisper “ooh i know it!” to themselves, but using a gesture of “quiet” and modeling my own fist to my chest was sufficient reminder for them to be thinking about strategies, holding their ideas private until called on.

After I saw that nearly every student had at least 1 finger raised (probably 45 seconds), I asked them to turn and talk to a neighbor about how they thought about the problem. The students did so well, and I heard many of them trying to explain their thinking in addition to sharing their answers.

After about 30 seconds of partner time, I called their attention back to me (I use “class class” –> “yes yes” call and response for this) and asked students to share answers. I called on just about every student and got 17 for all but 1, who said 14.

I then asked for volunteers to share their strategies.

The predominant strategy students shared was counting on, either from 8 or 9, using fingers. Two students adjusted and compensated – one by solving 9 + 9 and removing 1, another by taking 1 from the 8 and adding it to the 9 to make the problem 10 + 7. The last strategy (bottom left) was contributed by my coteacher.

Overall, this number talk was a great start to our summer school theme of using number talks in regular instruction to work on the OA strand. I’m looking forward to Monday!



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