#### cantsleep

##### Headphoneus Supremus

the rule states that we do multiplication/division before addition/subtraction. but why?

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multiplication before addition

- Thread starter cantsleep
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the rule states that we do multiplication/division before addition/subtraction. but why?

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

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Originally Posted by Duggeh /img/forum/go_quote.gif |

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

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Division is the same as multiplication by a reciprocal.

X/Y = X * 1/Y

Thus, the order does not matter.

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

EDIT: I agree, Febs.

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Originally Posted by Wodgy /img/forum/go_quote.gif If this bugs you, get a Reverse Polish Notation (RPN) calculator and control the order of operations yourself. |

x2, well said

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In Australia we were taught BODMAS

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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.

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

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Originally Posted by Arainach /img/forum/go_quote.gif ParenthesisNegation (the unary - operator)Exponentiation/RootsMultiplication/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...

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