Day 37: Absolute Value (again)

I’ll be honest; I didn’t nail absolute value this year. I loved the activity and will do it again next year. However, in less than a month students totally spaced the rules we had covered. AND I had an uneasy feeling in my stomach with the thought of moving forward.

I put these up on the board today as review


Students has a solid understanding of the first two. Half the class could work through c then only a handful were correct on d.

This is a huge red flag, if I let the slide absolute value inequalities would be a train wreck. Here’s the deal; it would be an awful idea to move on and try and force feed the rules of absolute value inequalities. So, I decided to start from the beginning again.

Thankfully Fawn Nguyen has an awesome post on absolute value that was a life saver and here is how I worked through the lesson today.

We started with the idea of distance;


Then eventually added some notation to the thing. There were some great discussions on how distance is always positive and how to work around the whole -4 – 8 thing.


After this point I stopped and really drilled students on translating what the above statements were actually saying. More than just The absolute value of negative six minus four is 10″ and asking students to think about this more as a distance thing.

“The distance between negative four and six IS 10”

My lesson on translating from earlier this year really helped when we jumped to this sorta thing:


The one issue I had here was it felt like students quickly shifted from thinking about absolute value as a distance to a rule where you take the number inside the absolute value and move 6 units to the left and right. Not sure what I think of that right now… I probably could have put more emphasis on translating but it just didn’t feel natural.

We practiced a few more of these then got into some interesting cases:



Tomorrow we are moving into absolute value inequalities continuing along with Fawn’s ideas. I really enjoyed this lesson!

*I missed my first post yesterday… I was out of the classroom again and driving for 9+ hours. 😦


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