Thursday, March 22, 2018

Math Memes and Order of Operations

Ok guys, you've seen these, you've likely commented on them...and every once in a while you actually hoped that the majority would get them right, only to be disappointed. What am I talking about?

Math Memes that broke the internet. They seem to be everywhere, Instagram, Facebook, Twitter, and the rest. And they always seem like a simple math equation or expression that everyone (at least everyone who made it passed 6th grade) should be able to answer with ease...but they DON'T. I even recently saw one posted in a Math educator's group, and even THEY couldn't agree on the right answer.

I have no idea who the original poster was, but it's on Facebook somewhere!

Most people today blame the "New Math" or "Common Core," they say things changed...But we all know they didn't. SO what really is the problem? Why do some arrive at the answer 24 while others get 6? And more importantly, how can we nip this problem in the bud before no one can get to the right answer?

We all learned the acronym in school, we know how to do this! The letter stand for: Parenthesis, Exponents, Multiplication, Division, Addition, Subtraction....That means we just work the problem in that order. So it look like this:
60/5(7-5)
P first = 60/5(2)
M next = 60/10
D last = 6
Problem Solved!

Not so fast! Remember, some got the answer 24...But how? These math minds are remembering a part of the rule that many tend to forget. We drill that acronym into students  minds, so they think its static...but it's NOT! No. The sub-rule is a left to right order...Yes, the inverse operations are worked TOGETHER in the order they appear in the equation/expression. So Multiplication and division are worked together and addition and subtraction are worked together. So for this particular problem, the acronym would be more accurate if it were written PEDMAS. Sometimes you might even do multiplication, division, then multiplication AGAIN ;) Here's a more accurate image to help sort this out: 

60/5(7-5)
P first = 60/5(2)
D next because it's first = 12*2
M last = 24
That's it! Now we have it!

Here's another one that blew up the internet about 3 years ago...

Again, no idea who the original poster was, but this is everywhere now.
Can you solve it? Leave your explanation in the comments.
Have questions? Ask them in the comments and I'll try to help you sort it out. 

Want to help me clear this confusion up, once and for all? Download the free poster and practice page by clicking the image above. OR, head over to my store and grab a copy of the full unit. It doesn't matter what age you are teaching, or tutoring, no one is "too old" for this lesson. Clearly, otherwise the internet would have solved it years ago! If you and your students would like a little more practice you can pop over to my store and gab a copy of How to Use PEMDAS. Thank you for your support!

 Order of Operations Made Simple


4 comments:

  1. I couldn't agree more. I will probably remember PEMDAS until I am old and gray, but no one bothered to tell me about the left to right rule. I am pretty sure my 8th grade algebra teacher got this one wrong too, but that was like 9 zillion years ago, so who is to say. It is also a pet peeve of mine when people say "new math". It's just math.

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  2. As English person and I've always had trouble with math, but after all those years of working with middle schoolers, I've finally got down those basics. Yay for PEDMAS!

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  3. As English person and I've always had trouble with math, but after all those years of working with middle schoolers, I've finally got down those basics. Yay for PEDMAS!

    ReplyDelete
  4. Definitely saving this for next year when my kid's math will require PEDMAS!

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