Let's talk addition!

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SWBAT share multiple methods to do mental addition of whole and rational numbers

Big Idea

Improving number sense and using number properties

Intro & Rationale

Warm Up

15 minutes

Today's warm up is looking for mistakes in our math family's homework from last night (included in resources). I display wrong answers that I got by making common expected mistakes on the screen for them to look for in addition to disagreement amongst the group:

1) 390 2) 102  3) 25 , 2 , 1  4) 1 , 12  5) 5  6) 51 , 149 , 24  7) 37 , 67  8) 30 , 225 , 15 

9) 270 , 70  10) 9 , 1

This was a process that we learned in a previous lesson ("conversation moves" lesson earlier in this unit ). Then I give them correct answers to check on a partners paper then work together to learn from their mistakes. I call this "growing their brain" time, because they are learning from their mistakes and the mistakes of others.

Number Talk whole number addition

39 minutes

I started this first number talk by telling students briefly about why we will be doing them, that I want them to let go of the idea of looking for the "one right way" and try to pay more attention to their intuition about the number relationships. I want them to let go of the years of negative self talk about math. I have them pack everything up and use only their beautiful brains. I remind them to stay silent while working the problems mentally so everyone can concentrate. They signal silently to me without raising hands up to avoid distraction and intimidation. Thumbs up means "I have a solution", "pointer finger means I am working on a strategy, but I don't have a solution yet", "two fingers means I have two strategies".

The problem string I used for this first number talk was:

57 + 10

57 + 9

57 + 19

57 + 49

46 + 99

215 + 495

4.9 + 3.2

We did one problem at a time. I asked for solutions first, then strategies. My goal is to highlight multiple methods: MollyMei LinJohn, & Angelina each share different methods. I modeled their methods numerically as well as on an open number line. I also put their name next to it to give them some ownership and so others could easily reference the methods of others.

You will hear a boy, Brandon, off camera disagreeing with his first answer so I give him the first oportunity to explain what he had been thinking that caused the error and then his strategy for arriving at his new answer. Throughout the video you will see Angelina persists in using the counting on strategy until 57 + 49 when she says "oh, I can't use my strategy on this one" and tries one of the other ones she's seen from her peers (although she doesn't let go of counting completely).

 At one point I shushed Jose only to find out on the video that he was so excited about being able to do the problem in his head that he wanted to talk about it with his math family. One special ed student in the corner was celebrated for sharing the correct solution. Too bad we can't see her face in the video! This was a girl who had her head down or was looking away during the first few problems and had already demonstrated within the first week of class that she had no confidence in her math ability.