Why does PEMDAS work?
Date: 7/9/96 at 14:29:37 From: Anonymous Subject: Why PEMDAS? Dear Dr.Math, I am having trouble with a few problems that involve PEMDAS (Parentheses, Exponents, Multiplication, Divison, Addition, Subtraction). The real question I have is why does this order of operations really work? Thanks a lot, Kathleen
Date: 7/9/96 at 17:45:7 From: Doctor Ceeks Subject: Re: Why PEMDAS? Hi, When you ask "why does this order of operations really work?", you are asking something which suggests a slight misunderstanding about math. The order of operations in which one is to interpret a mathematical expression such as "2+3 X 5" is a convention. This means that a long time ago, people just decided that the order in which operations should be performed should be such and so. It has nothing to do with magic or logic. It's just that some people decided to adopt a way, and it has stuck ever since. It just makes communication a lot easier. It's just like asking, "why is it that when I say 'cow', people tend to conjure up an image of a beast in a field, possibly with spots?" Well, it's because a long time ago, someone decided to call that beast a cow. Now, everyone who speaks English knows this and so if you want to make someone think of the big beast, you just have to say "cow" to them...how efficient! It has nothing to do with the poor little grass eating creature...it just has to do with what people have agreed upon to make communication with each other a little easier. So the answer to your question is that it works because you're just learning how to interpret math formulas the way people have long decided to interpret them. Now, if you're having trouble learning the order of operations, then you have to remember that you're not having a problem with mathematics (unless you're getting wrong answers because you're adding incorrectly). What you're having trouble with is learning a convention, like learning the grammar of a foreign language. Because it's just a convention, learning it is just a matter of practice, practice, practice. Start slowly and carefully. Eventually you'll have it memorized. -Doctor Ceeks, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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