The only bit of math I have retained is that order in which you solve expressions, only because it fits neatly in the language hemisphere of my brain because of the mnemonic device "Please Excuse My Dear Aunt Sally" (Parentheses, Exponentials, Multiplication, Addition, and Subtraction. Spoiler: This is a lie.)
I can remember the mnemonic because my left hemisphere works. I would comfort myself that math pros can do the math but can't remember the mnemonic. Hahahaha: justice. Then I remember Friend #4 who can write and calculate in her head simultaneously.
So, intermittently on Facebook you'll see a question like this:

Then, in the comments you'll see a variety of answers, each insisting they are right. I felt confident I could get it right, because I had my dear Aunt Sally to guide me, especially since there were no parentheses or exponentials. (It's odd that in English a parenthesis connotes a topic is less important; in math it is most important. I wonder if people who use both hemispheres read this parenthetical statement at the top of their lungs instead of the confidential tone I use to write it.)
I wasn't brazen enough to share my answer the entire world on Facebook; I just sent it to Friend #4, and let my friends see it.
Five, I said.
Hot Mom immediately commented that she and her eleven year old daughter both got seven, how did I get five?
I replied:
My: 6-(0)+2/2
Dear: 6-0+(1)
Aunt: 6-(1)
Sally: 5
Logic!
Friend 4 replied that no, seven, and here is why:
P - Parentheses - Left to right, solve all parentheses first.E - Exponents - Left to right, solve all exponents.MD - Multiplication and Division - Left to right, solve all multiplication and division in the order they appear. They have equal weight, so do not skip division to do multiplication later in the expression.AS - Addition and Subtraction - Like MD, they have equal weight, so solve them left to right.
This concerned me, not only because now I can't do fourth grade math, but I was concerned about the Middle East and wherever else they read right to left. How confusing must that be? They would be hard pressed to answer five as well, because the subtraction is on the right.
What we need is a new mnemonic, one with four words instead of six. (I almost wrote "seven words," then I counted on my fingers.) But in the third word, there must be an M and a D, in that order (left to right). Similarly, the fourth word needs to have both an A and an S.
I've got "Please excuse MacDuff's ASpirations," which doesn't make sense because it was the Macbeth's who were ambitious. "Parents enjoy McDonalds' .... Apple Snacks?" No that's two words. AppleS? No, that S is too easy to ignore.
Piggies Exhibit McDonalds Ass?
I like that one but it won't play to the fourth graders. It's too declarative as well. Aunt Sally had a little mystery to her.
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