PEMDAS:What does it stand for?

Re: PEMDAS:What does it stand for?

It's an "acronym" that is supposed to remind us of  the "correct" "order of operations".......it stands for

Parenthesis

Exponents

Multiplication

Division

Addition

Subtraction

However,  this "order" isn't exactly "correct." Many students think they're supposed to always perform "Multiplication" before "Division" and "Addition" before "Subtraction."

A more "correct" order of things would be

Parenthesis (or Brackets)

Exponents

(Multiplication    Division)   or  (Division  Multiplication)

(Addition    Subtraction)    or  (Subtraction  Addition)

The first two liness should be self-explanatory....work inside any parenthesis first and then apply any exponents!!

The last two lines require some explanation. Multiplication and Division are performed at what is known as the same level of "precedence." This means that we perform these operations as we encounter them from "left to right." The same thing applies to Addition and Subtraction.

Let me demonstrate what I'm talking about - first with Multiplication and Division, and then with Addition and Subtraction.

Let's supppose we have this :

36 / 9 X 4

Many students assume that they're supposed to perform the "multiplication" first and then the "division.'

So we get (wrongly).....  36 / 36   ..and then, "dividing," we have the "answer'....."1"

This is incorrect...we perform any multiplication or division as we encounter them from "left to right."

Correctly...we would have .....36 /9 = 4 and multiplying this by 4  we obtain 16. Note that that's a lot different than "1.'

Addition and Subtraction behave the same way. Suppose we have:

14 - 3 + 10

Uising the "incorrect" way, we would add the 3 + 10 to get 13, and then subtract this from 14 to get '1.'

The correct way is to evaluate (14 -3) first - (11) - and then add this to (10) getting 21. Note that that's a different answer from  "1.' 

Oddly enough, the beginning maths seem to make this more difficult by their reluctance to use any parentheses (or brackets). I don't find this to be true of the higher maths - In these, it's usually explicitly spelled out what's to be done. Take, for example, the addition and subtraction problem we just did.

The "lower maths" tend to write it just as we did, i.e.,  14 - 3 + 10. In the upper maths, it would be written as (14 -3) + 10. Note that there is no confusion about what to do here.......the operation inside the parenthesis is done first, and then the "10" is added to the result !!!!

Also.....note the confusing nature of something like the following:

3 x 6 / 10 + 8 - 4 / 2

....Ouch!!....that makes my head hurt just looking at it !!!

This is far easier to understand:

[(3 x 6) / (10) ] + 8 - (4/2).........don't you agree ???

Yep....I'm long-winded !!!  ....but, I hope this helps !!!

parenthesis, exponents, Multiplication, division, addision, subration

I am just going to add a little bit of trivia.   

i had never heard of PEDMAS untill I started foruming (7months back).

In Australia we call it BODMAS  

B for Brackets, O for of (meaning, power of) the rest is the same.

Parenthesis are just the curly brackets that arn't used much.

Exponents is not a word used much in Australian schools - we just call them powers.

I don't know why BEDMAS is not used - maybe it would bring on too many snickers in an adolescent classroom. (I am sure many would find it very funny - it is  bringing a smile to my face, I admit it) 

IT MIGHT BE EASY TO REMEMBER THOUGH!