Please Excuse My Dear Aunt Sally might sound sort of confusing, but the Order of Operations is just the opposite. This video explains PEMDAS, the rule for remembering how to solve a complex equation in the right order to ensure the correct answer every time.
Algebra is no different. There is a right and wrong way to do things, and a proper order [Toilet with an out of order sign]
in which to do them.
To remember what that order is, we use an acronym called PEMDAS. [Cheerleaders in formation]
It stands for “parentheses,”…
…“multiplication and division,”…
…and “addition and subtraction.”
It does NOT stand for Private Eye Makes District Attorney Sad.
But if it helps you remember the acronym, more power to you. [Judge banging gavel]
Let’s see it in action. Take the problem 5 minus 3 plus 6 divided
by 2 plus the quantity “7 minus 5” squared.
According to PEMDAS, first we have to take care of those pesky parentheses. [numbers in parenthesis highlighted]
Easy enough. 7 minus 5 isn’t rocket science. Good thing, or there would be far too many [rocket preparing for launch]
rocket scientists flooding the job market.
If we rewrite our problem, we get:
5 – 3 + 6 ÷ 2 + 2 squared.
Next we have to rub out any exponents. That fella on the end is the only exponent, so [exponent highlighted green]
let’s actually square “2” and send him on his way.
Now we’ve got 5 – 3 + 6 ÷ 2 + 4
There’s no multiplication, but we do have a tiny bit of division to perform.
“6 ÷ 2” gets our attention first – so says PEMDAS. [Man tending to PEMDAS's needs]
Yeah, we pretty much do whatever it tells us to do.
We can rewrite our problem as 5 – 3 + 3 + 4.
Addition and subtraction hold equal weight… [Addition and substraction in a weighing scale]
…so we can just perform all remaining operations from left to right to give us our final answer:
which is 9.
Quite a bit different from the answer we would have gotten if we’d done everything from
left to right.
Here, at least, different is not good.
No matter how stylin’ you think you look in your shoe-socks. [Person takes socks off their shoes]