(Originally posted to Mom on a Narrow Path blog on Weebly, now deleted.)
As I have said before, I am currently in a college mathematics class and we are revisiting/refreshing pre-algebra knowledge. Our Dear Aunt Sally has shown up repeatedly. In an effort to introduce my son to the types of math he will some day be expected to calculate, I brought up Aunt Sally.
Granted, he is only in the fourth grade, however, I do not think it is ever too soon to share the wonder and awe of higher learning elements. I walked him through what the phrase actually stands for by talking about acronyms. He understands acronyms, of course, from SHIELD (Strategic Homeland Intervention, Enforcement and Logistics Division), HIVE (Hierarchy of International Vengeance and Extermination), STAR Labs (Scientific and Technological Advanced Research Laboratories), ARGUS (Armed Revolutionaries Governing Under Secrecy), HAMMER (meaning unknown), and of course TMNT (Teenage Mutant Ninja Turtles).
PEMDAS, or "Please Excuse My Dear Aunt Sally", needs to come with a little teaching, not thrown in the garbage. The memory trick worked fine for generations, yet many mathematicians are cringing at its continued use. Google "Please Excuse My Dear Aunt Sally" and you will come across an Education Week article by David Ginsburg, excusing Aunt Sally forever - forever out of use in Math class.
Most of my fellow college classmates are quite aware of PEMDAS as we are the generations who were still taught order of operations via this acronym. The crazy thing to me, is that somewhere along the way, kids got confused or teachers failed to express a fine point of "Left to Right". I did not want to completely confuse my son, so I left out much of how to use PEMDAS for now, opting to just explain what it is and what it stands for.
I really do not think it fair to toss Aunt Sally to the side. For starters, Aunt Sally did nothing wrong. The teachers were wrong to assume that using her without guidance was okay. You can not just throw PEMDAS at students and expect them to understand every aspect and rule of it.
When I wrote PEMDAS out on my paper with my son, it read as follows:
Please = Parentheses
Excuse = Exponents
My Dear = Multiplication & Division
Aunt Sally = Addition & Subtraction
Now honestly, I do not remember my teachers explaining it in any other way. They told us that you do multiplication and division together from left to right, just like we read, and then addition and subtraction in the same way. For this reason, they did not write the last two-thirds on four lines, but two.
So why, exactly, are kids getting the impression today that they are to do them separately? Why do they think that 4 - 2 + 1 equals 1?
Do not penalized Dear Aunt Sally for teachers' inability to effectively teach.
