[cantsleep]

very simple. 2+2x2=6, not 8
the rule states that we do multiplication/division before addition/subtraction. but why?

 

[Wodgy]

Because it's a convention to avoid fully parenthesizing expressions. Nothing more. The convention could be anything you like.

If this bugs you, get a Reverse Polish Notation (RPN) calculator and control the order of operations yourself.

 

[pez]

Well usually when you see a problem like this it is divided by parenthesis. I'm sure you are familar with PEMDAS or as some refer to as Please Excuse My Dear Aunt Sally. Since these are usually placed inside parenthesis, and the rule states that you do the parenthesis first, you would have to what's inside them first, which in this case is (2x2). After that is solved, the parenthesis are negated and you can then find the final solution.

 

[Duggeh]

PEMDAS? I was taught BODMAS (brackets, order, division, multiplication, addition, subtraction). Whats PEMDAS? (parenthesis, exponentials, multiply, divide, add, subtract)?

 

[Mher6]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif PEMDAS? I was taught BODMAS (brackets, order, division, multiplication, addition, subtraction). Whats PEMDAS? (parenthesis, exponentials, multiply, divide, add, subtract)?

Yep, that's what PEMDAS is and that's the way I was taught.

 

[DNT]

So PEMDAS and BODMAS are two different systems? One says division first and the other says multiplication. So which one is conventionally correct?

 

[Febs]

Multiplication is cummutative. In other words, the order may be changed without changing the result.

Division is the same as multiplication by a reciprocal.

X/Y = X * 1/Y

Thus, the order does not matter.

 

[The Actual]

^division is multiplication by a reciprocal. Either system is left to right with division/multiplication.

(x*y)/z=x*(y/z)=x*y/z




EDIT: I agree, Febs.

 

[shellylh]

Quote:

Originally Posted by Wodgy /img/forum/go_quote.gif Because it's a convention to avoid fully parenthesizing expressions. Nothing more. The convention could be anything you like. If this bugs you, get a Reverse Polish Notation (RPN) calculator and control the order of operations yourself.

x2, well said

 

[d-cee]

In Australia we were taught BODMAS

 

[Arainach]

It's not a Linear Order, it's a Heirarchy. The standard system goes something like (top is highest priority):

Parenthesis
Negation (the unary - operator)
Exponentiation/Roots
Multiplication/Division
Addition/Subtraction

And, if one gets into programming, below this comes the bitwise shifting operations, than the comparative operators, than the bitwise logical operators, than the various logical operators.

 

[FallenAngel]

PEMDAS, BODMAS, meh, in Ukraine we were taught to remember the order of operations with a ruler across the hands. It's effective and you remember damn well.

 

[Born2bwire]

Because we're forward thinking Americans, not like those silly Polish.

 

[goldenratiophi]

Quote:

Originally Posted by Arainach /img/forum/go_quote.gif Parenthesis Negation (the unary - operator) Exponentiation/Roots Multiplication/Division Addition/Subtraction

huh? Negation is just multiplication by -1. If negation is to be read first then you'd have -5^2 = 25. However we write -5^2 = -25 and (-5)^2 = 25. Unless I'm misinterpreting what you mean by negation...

 

[K2Grey]

I thought negation was used for like, boolean operations. Granted in that case it's unclear to me how it would interact with multiplications and divisions and so on. Ahh, math, you can get ridiculously complicated.