While “My Aunt Sally” only has good intentions to help us remember the order of operations, this mnemonic actually ends up hindering some of us along the way…. and so does the acronym PEMDAS.
The order of operations is actually:
- Complete what’s inside the grouping symbols. We are taught to look for parenthesis (hence the Please in Please Excuse My Dear Aunt Sally) when we’re first learning how to do the order of operations because parenthesis are the most simple form of grouping symbols. However, grouping symbols also include brackets and the division bar but somehow these get overlooked. Maybe we should’ve called this Golly Excuse My Dear Aunt Sally.
- Exponents. Complete all exponents. If there is more than one exponent in a problem, do what’s inside the grouping symbols first and then move from left to right.
- Multiply and Divide in order from left to right. When we are first learning how to do the order of operations, our teachers only give us problems where multiplication is on the left of division in the problem, or there is only one of these operations in the problem. They think they’re being helpful, but in reality it doesn’t help us understand the fact that you’re supposed to do these two things in order from left to right. Instead of this helping us, a good chunk of us end up thinking we always do multiplication first…but that’s not at all the truth. The mnemonic could’ve very well been Please Excuse Dawn Mary And Sam!
- Add and Subtract in order from left to right. The teachers used the same teaching ideas with Addition and Subtraction. We’re supposed to do whichever one comes first when reading the problem from the left to the right, but many of us think we always have to add first… all because of Aunt Sally.
While we all know that Aunt Sally only has good intentions, we also know that she can be a tricky devil. Don’t let her or PEMDAS ruin a good math problem for you!