This was a GREAT lesson for students that were already familiar with adding and subtracting negative numbers. I am also going to use it with my new 6th graders that have not used negative numbers before, but only after introducing them to positive and negative numbers with the number line and with positive and negative integer chips.

I saw an amazing video of Allison Krasnow on the teaching channel that explains this activity really well. So, if you are interested in this activity, I strongly suggest that you watch her make the magic happen! Also, she recently blogged about it, with improvements! So, go read it! Coincidentally, I also hosted one of Allison’s post when she joined the “New Blogger Initiation” last month! I just didn’t put two and two together until I was looking her up to give her due credit for this fabulous activity! It is really a “small world” with math teacher bloggers – hurray!

For this activity, students use three circle stickers. Yellow for the final sign (they put this on first), green stickers for positive numbers, and red stickers for negative numbers. We just learned absolute value so I had them put the number with the larger absolute value “on top” because this also helps to ensure that they do the subtraction algorithm correctly. The sheet I created is at the bottom.

I was worried that my seventh graders would not get into this activity and actually debated doing it with them. I knew I wanted to do it with 6th, but 7th has practiced and practiced and practiced negative numbers last year. However, I still have a couple of students that have trouble, and it seemed like such a great idea so I went for it.

I am so very glad that I did! First of all, the kids were obsessed with the stickers. They really loved using them. This surprised me because they are just plain dots that you get at office supply stores. But, the best surprise of all were several of my students saying, “Wow! This makes so much sense now! Can we always use these?” I then told them that they can use red and green colored pencils on their homework if they would like to!

I also asked them to find a person who they thought worked “at the same pace” that they worked. This worked GREAT because I wanted them to do partners for this activity, but not have one person “telling” the other what to do or what the answer was. This way one my more proficient students finished, they could move on to another activity (Zero is their favorite). I loved that students really embraced this, even moving after they got started because a group was going “too fast” or “too slow” for their pace. I’m going to do this much more in the future!

Thanks Allison! And welcome back to blogging! 🙂

Really like this idea – I watched the link on the teaching channel too and I think it is a very successful method. Where I am getting stuck at the moment is embedding the understanding for subtracting a negative….how do you explain this?? I have used a number line and the notion of adding cold, subtracting heat, subtracting something cold for students to think about the effect of the signs, but still doesn’t seem to be sticking…..

Dee,

I created a video on understanding zero pairs for my sub to show the students. At the 1:37 mark it explains subtracting a negative. http://www.youtube.com/watch?v=zqt-fxcUPek&feature=plcp As an in class follow up I talked about how zero adds no value, but we use it when dividing, say, 2 divided by 5. Ask Dr. Math http://mathforum.org/library/drmath/view/57870.html provides a few real world examples. The concept is challenging!

Thanks for those links Mary – it always great to see different ways of explaining things! I will definitely try these out next time I revisit the topic, and hopefully something will have the ‘penny dropping’ moment with the kids! Thanks again!

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