Re: Please don't ask the same question in three threads Message #7 Posted by Matt Kernal on 22 Feb 2001, 6:19 p.m., in response to message #5 by Mike Burns
Mike Burns> Therefore; is there a rule of thumb?
I hope I'm correctly understanding the question you're asking, but beyond having balanced parentheses, yes there is a rule of thumb. Call it what you like, order-of-operations, priority, or precedence, the memory aid I remember is.. PEMDAS (Please Excuse My Dear Aunt Sally) where:
P = Parentheses
E = Exponents
M = Multiplication (same priority as division)
D = Division (same priority as multiplicaton)
A = Addition (same priority as subtration)
S = Subtraction (same priority as addition)
Which means "before anything else, do what's inside the parentheses. Next, if there are any exponenents, apply that power to the result of what was inside the parentheses. Next, if there is a division OR multiplication, apply that operation next. And finally, if there is any addition OR subtraction to do, apply it last".
On a related note to Dave... I noticed your description of the HP-17B calculator mentions it has "full algebraic logic including precedence". By accident, I found mine doesn't recognize precedence. Recently, HP's Jean-Yves Avenard pointed that only the algebraic scientifics recognize precedence (like the 6S, 20S, 21S, 22S, 27S, 30S, 38G, 39G), but the algebraic business calculators do not (17B, 17BII for sure; I haven't tested the 10B, 14B, 19BII). I asked him why the inconsistency? After all, they aren't called "calculators" for nothing. He said it was an industry standard; Ti and Casio do the same. I haven't noticed if this is actually true.
To be safe, know your order-of-operations, and never stray away from RPN :-)
Matt
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