Critical Thinking With Real Life Math

Anyone who knows me know that I’m very much about critical thinking in all subject areas.  Many people tell me that it can’t be done in math because critical thinking is all about asking questions that have no real “right” answer.  They argue with me that in math it’s either right or it’s wrong.  Here’s an example of what happened in my Grade 8 math class today that proves what I’ve been trying to say.

We’ve been talking about percents in class, specifically discounts.  I told my kids today about a real situation that happened to me just this morning.

I went and bought my little girl a Christmas dress yesterday.  I splurged because she has so many hand-me-downs that I next to never have to buy her clothes so I let myself indulge a little this time.  From Gymboree I bought:

A dress – $69.50

A hat – $18.50

Tights – $9.00

And then the thing that I most hate when it comes to shopping happened to me this morning.  The store sent me an e-mail advertising all their “holiday styles” now at 25% off.  Grrrrrrr……….

So I put it forth to the kids: “IS IT WORTH IT TO GO BACK FOR THE REFUND?”

Several good questions came out of this such as, do we have to calculate the discount on each item individually or can we just have a grand total?  How far away is the store?  Shouldn’t we take into consideration the cost of gas?

Wow…..I love my kids.  In the end they figure I got gypped out of $22.50 (I told them to ignore GST for now).

So there’s a math component (which is the “right/wrong” part I guess.)  But that’s not what I cared about. They were all within the ballpark and most of them nailed it right on the head.  What came next was the best part of the question.

They said that while the $22.50 is a lot of money, if it costs you $15 in gas then you really only wind up saving around $7.00.  And is it worth two hours out of your day to do that?  You’ll have to take your little girl and she might be cranky and hard to put up with.  You’ll probably wind up having to buy food while you’re there and you might just buy something else that you wouldn’t have otherwise.  All in the name of $7.  This group decided, forget it….not worth it.  It sucks, yes, but in the end you could wind up losing out on more money.


You had to be in the area anyways….(which I do because I need to go to Costco, which is right there) and in that case you wouldn’t take the gas money into account because you’d be spending that gas anyways.

So they’ve decided I should go get the $22.50 back and spend it on shoes.

I like the way they think.  I had forgotten to buy shoes to go with the outfit anyways.

I relish any opportunity to brag about my Grade 8’s and I thought their reasoning skills really showed through today.  Critical thinking can take place in math.  Perhaps the actual physical math answer is right or wrong, but you can ask questions for them to reason through that can be supported with the mathematical process.

I would like to think my kids were much more engaged by the question “Is it worth it to return it?” then they would have by the traditional question they would normally see such as, “How much money could I have saved if I had bought the items on sale?”  One does indeed have a correct answer, the other requires some thought and reasoning with support and evidence.  I know which question sounds more interesting to me!

Critical thinking in math isn’t so much about the final math answer, it’s about taking that answer and using it to support a question that has some actual relevance.

About Cherra-Lynne Olthof

I've been a middle school teacher for my entire career (which began in 2001). Like my students, I too am a life long learner. My goals include helping my students to achieve their goals, support them in their learning, and to encourage them to think "beyond the grade".
This entry was posted in 180 Days of Teaching, Critical Thinking, Math Reasoning. Bookmark the permalink.

3 Responses to Critical Thinking With Real Life Math

  1. Nordin Zuber says:

    Love it! I’ll be looking out for similar opportunities. A side note: you might be interested in the etymology of the word ‘gypped’. Check it out. I thought it came from the experience of soldiers visiting Egypt during WWI, but it seems not. Thanks for the posts and love your blog.

  2. Carlita says:

    Nice article. Its realy nice. Many information help me.

  3. Pingback: Why Inquiry Based Learning is Not Discovery Learning | Teaching on Purpose

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