Critique the Reasoning of Others…a 5 minute math lesson plan

So I just wanted to share a super quick math lesson plan idea that you might want to try.  It was NOT in my plans, but I saw that a ton of my students made errors on a decimal number line problem and I knew I needed to do something ASAP.  Those Standards for Mathematical Practice are SO important, so I took this opportunity to really give my students some work on critiquing the reasoning of others!
standards for mathematical practice

First…I grabbed the pile of papers and divided them into piles of students who got the same or similar answers.  I then grabbed three pages off of different piles to form trios of students who had DIFFERENT responses.

critique the reasoning of others
Why?  I wanted to get them talking!  We have worked hard on creating a climate where students welcome feedback from others and understand the purpose–and it’s a good thing because there was a TON of feedback being given!

The task!

Their task?  CLEARLY explain why they assigned a certain decimal value to the point on the number line and then be able to defend it when the others ask questions.  The others in the group?  Try to find misconceptions and errors and politely make their point to try to convince others to adjust their answers.
My rule?  No pencils allowed–just highlighters.
standards for mathematical practice

My reasoning here is that I want students to be ok with being wrong…that FINDING mistakes and misconceptions is the game…not getting the right answer.  With pencils, the temptation to “alter” responses is too great–and it isn’t where the learning happens.  I have taught my students about the brain research (If you haven’t read Mathematical Mindsets by Jo Boaler RUN to go get it.  I’ll throw in an affiliate link at the bottom of this post if you want it.  It is a game changer) that simply making mistakes grows brains.  If you can FIND them, the learning is magnified.  We celebrate them!

I had so much fun walking around and listening to the discussions/explanations/debates and watching students really use their number sense to help their classmates clarify their thinking.  I did this lesson with number lines–but there are a ton of other ways this could be done in other contexts.  It was great to hear the students really using their decimal knowledge to explain how they used benchmark numbers and divided their number lines into different segments.  Like this math lesson plan idea? Give it a try!
critique the reasoning of others
If you are looking for number line resources, here are the three I have at this time.  Each is separately linked to this posting as well.
number line activities
Want to pin this post for later?  See the pin image below.
And last but not least…the AMAZING book by Jo Boaler…some of the best $12 I’ve ever spent.  For real.