Comparison Subtraction in Action

Written by Donna Boucher

Donna has been a teacher, math instructional coach, interventionist, and curriculum coordinator. A frequent speaker at state and national conferences, she shares her love for math with a worldwide audience through her website, Math Coach’s Corner. Donna is also the co-author of Guided Math Workshop.
In my role as a campus-based math instructional coach, I work mostly with teachers–assisting with planning, providing professional development, modeling, etc.  But I also get to work with 3rd and 5th grade students as part of the Learning Together program.  In this peer tutoring program, 5th grade students tutor 3rd grade students in math.  Very neat program!  Yesterday, I had my Scholars Institute with the 3rd grade tutees, and I had planed an icebreaker activity called Would You Rather?  Basically each kiddo writes two options on an index card, for example play outside or read a book. I collected all the cards and for each card, I read the two options, held out my arms, and the kiddos moved to the side they would choose.  So, you might end up with four kiddos on the play outside side and six on the read a book side.  I hadn’t meant for it to be a math activity, but it seemed too perfect for comparison subtraction to pass up!  
With the four on one side and six on the other, I asked, “How many more of you would rather read a book than play outside?”  What do you think the first answer (from pretty much all of them…) was?  If you guessed six, you’d be right.  That is the most common wrong answer for comparison subtraction–instead of looking at only the difference, they just tell you the bigger number.  So, one-by-one, I moved the kiddos from the play outside side to stand next to a kiddo on the read a book side.  Then I asked again, “How many MORE of you would rather read a book than play outside?” Still six.  So I showed how each of the read a book students had a play outside partner right up until four, but that two MORE students had voted for read a book. Ah!  Light bulbs!
We continued going through the cards they had written, acting out the comparison subtraction, and it seemed to make a big difference in their understanding.
BTW, my favorite card…Would you rather drink spoiled milk or eat moldy cheese?  I saved that one for last!

13 Comments

  1. Anonymous

    awesome!!!!

    Reply
    • Donna Boucher

      Glad you like it!

      Reply
    • Christina Ranker

      The real world concept of the problem is excellent. Using a matching technique to compare those who chose going outside to reading a book makes the “difference” in the comparison problem very clear.

      Reply
  2. Lisa Lewis

    Thank you! Many of my third graders struggle with comparison subtraction so I’m doing this on Monday. Thanks again=)
    ~lisa
    TGIF-Third Grade Is Fun

    Reply
    • Donna Boucher

      Sure thing, Lisa! My pleasure. 🙂

      Reply
  3. msbeers

    This is a great idea! Any tips for teaching comparison subtraction to my first graders?

    Reply
    • Donna Boucher

      Actually, this would be a great activity for first graders! The third graders I’m working with are a bit below level.

      Reply
  4. Aggie Teacher

    This is so awesome. You have my exact job I want 🙂

    Reply
    • Donna Boucher

      I have to admit that I love it! So you realize you’re right down the road from me, right? My son attends A&M. 🙂

      Reply
    • Aggie Teacher

      I am actually near Microsoft near Seattle but I went to A&M so happy to hear your son is an Aggie! Whoop

      Reply
  5. Em Hutchison

    I am coming to see you in Baltimore. I am from Cincinnati…I can’t believe my school is letting me come. You have completely changed my math mind. And I am so thankful to come and listen to your speak!

    Em
    Curious Firsties

    Reply
  6. Kelly

    I love it! I love when you can combine two lessons in one! I wish you worked at my school. I have learned so much from reading your blog.
    Kelly
    I’m Not Your Grandpa, I’m Your Teacher

    Reply
  7. Mrs. Cockrell

    This is genius! Thanks for sharing!

    -Gayla
    Teach On.

    Reply

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