Monday, September 3, 2012

PEMDAS must die!

Here is my third blog post for the new math teacher blogger/twitterer initiation. My prompt is:


2. Your students come into class rife with misconceptions. EEEP! What is a misconception that you see a lot? If you haven't done so yet, brainstorm a way to deal with that misconception so that students will leave your class with that misconception fixed. (Or if you have a misconception that you deal effectively with, how do you do that?)


True to fashion, I will now sort of answer the prompt:


My buddy Andrew Stadel just made a great song about PEMDAS.



It is tough to write a math song that is not ridiculously cheesy. In fact, most math songs drive me insane. They're usually so terrible that I can't bare to force my students to listen to them. Of course, that doesn't stop me from making my own songs and thinking they're not cheesy. (The video below was made with the help of my eighth grade students last year.)



But I'm getting a little off topic here. I love Andrew's song. It's very catchy and I think I have most of it memorized. But I still hate PEMDAS. Every year I get a few eighth graders who insist that you always multiply before you divide. And you always add before you subtract. There is no doubt in my mind that the acronym, PEMDAS, is the culprit.

Once in a while students will even go so far as to tell me that I'm wrong and their teacher from last year is right. I then hand them a piece of paper with "18/6*3" written on it, tell them to go find their teacher from last year, and have them simplify the expression. The last time I did this, the paper suspiciously got lost in transit.

It takes a ton of warm-ups and review to finally break them of this dirty habit.

So I suggest...no more PEMDAS. No more "Please Excuse My Dear Aunt Sally". It only does more harm than good. We tell them to remember left to right, but they don't. They only remember PEMDAS.

Nathan Kraft