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In standard mode, the calculator appears to be evaluating all operations left to right. If you calculate 7 - 2 * 3, you get 15.OCR said:
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OCR
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Yeah, it is...Mark44 said:
In the scientific mode you get 1...
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"Over unity/PMMs."Chestermiller said:
OCR
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Yeah, I think they both have the same functions ...fresh_42 said:
https://en.wikipedia.org/wiki/Calculator_(Windows)#Windows_7
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Maybe it's just me, but does anyone else think significant figures as explained in a number of textbooks are a bit ambiguous? Something like, ##2.000(11.23 - 10.53)## could be interpreted as ##22.46-21.06## or ##2.000(.70).## Even beyond what I see as ambiguity, significant figures based on multiplication/subtraction/etc. are kind of annoying. It seems just as easy to teach propagation of uncertainty and get students use to seeing a number with it's accompanying error bounds. Although I can see the appeal to the quick and dirty method (it's quick).
Gold Member
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Wow. I've always been careful with using parenthesis on calculators but that is odd.OCR said:Who'da thunk it... ? ....
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I wouldn't have assumed it but it isn't surprising for a device with a certain amount of brain. I would always have put in the parentheses. The first proper calculator I used was an HP and Reverse Polish is still my automatic approach to calculations on a calculator with anything ambiguous about them. You can't go wrong with RPN (haha). It's good to know that the Scientific Calculator could store the whole expression before evaluating it. I wonder how long the expression would have to be to beat it.OCR said:Who'da thunk it... ? ..
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Borg said:
A possible explanation is that the average person using the normal calculator would never have heard of PEMDAS and expect those operations to be done left to right. This is the way it works in those arithmetic puzzles in the newpapers (where they do actually say: operations to be carried out left to right).
But, for people using the scientific calculator the dark cloud of PEMDAS hangs over them, so the operations are carried out in a bizarre order.
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Not really "bizarre". It's just following the rules for the shorthand way of writing down a calculation. It's 'grammar' for Maths.PeroK said:
I never trust myself with a long chain of key entries with no visual feedback, in any case. I like to write the expression down so I can see what I have done and then leave it to the processor to work it out. I was in a pub the other day and the barmaid got three different answers on three attempts on a hand calculator. I sympathised.
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sophiecentaur said:
It isn't really grammar for mathematics, it's grammar for certain arithmetic expressions that you never actually need. I did a degree in maths and have been studying maths and physics for 3 years now. I have no idea what PEMDAS really says and I've never found the need. No one uses these expressions outside of arithmetic classes to teach the rules of PEMDAS!
Still peeved!
The symbols ##\times## and ##\div## are not used in "proper" maths in any case. So, there need be no rules to govern their usage.
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This is my last post on the subject! And it's a serious one.
PEMDAS encourages students not to use brackets, but to rely on a convention that everyone else may or may not know exactly. This continues into their maths generally, so you see things like:
##\sin x + y##
This is partly the influence of teaching PEMDAS.
If, instead of PEMDAS, they were taught the importance of avoiding ambiguity in mathematics, this would be much better. And that is genuinely important to maths at all levels. They should be taught to use brackets whenever there is any room for ambiguity. The relevance of PEMDAS is short-lived and it teaches bad habits that are then much longer lived.
PEMDAS encourages students not to use brackets, but to rely on a convention that everyone else may or may not know exactly. This continues into their maths generally, so you see things like:
##\sin x + y##
This is partly the influence of teaching PEMDAS.
If, instead of PEMDAS, they were taught the importance of avoiding ambiguity in mathematics, this would be much better. And that is genuinely important to maths at all levels. They should be taught to use brackets whenever there is any room for ambiguity. The relevance of PEMDAS is short-lived and it teaches bad habits that are then much longer lived.
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Greg Bernhardt said:
Coming back to the original question of the thread, one of my biggest pet peeve is when I hear a non-scientist tells me "it's ONLY a theory!"
Zz.
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I prefer trees. It's my favorite response to an answer like: "5" - "5? 5 trees, or what?"ZapperZ said:
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Meanwhile I think, this must be actually a disease, like dyslexia or dyscalculia. Maybe, it's a hope of mine.DrClaude said:
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So, ##\log_2 32 = 5 \text{ trees ?}##fresh_42 said:
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Maybe it is a good idea to stipulate in the homework template that problems may only be posted in non-dimensionalized form 
.
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Ahh, that's where you are wrong my boy.PeroK said:
3p+2q makes sense to you, dunnit? That implies an unconscious use of PEDMAS etc., whether or not you are explicitly aware of it. You could expand on PEDMAS /BODMAS by putting a big 'F' in front of them, meaning Functions.
Familiarity breeds contempt.
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Let's write ##3x^2 + 5x + 7 = 0## without PEDMAS:
[tex](((3\cdot x)\cdot x) + (5\cdot x)) + 7 = 9[/tex]
Don't know about you, but I prefer to have this whole PEDMA convention...
[tex](((3\cdot x)\cdot x) + (5\cdot x)) + 7 = 9[/tex]
Don't know about you, but I prefer to have this whole PEDMA convention...
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Well almost. But at least in terms of quality.Mark44 said:So, ##\log_2 32 = 5 \text{ trees ?}##
I found ##\ln V_t = 1.34 + 0.394 \ln G_0 + 0.346 \ln t +0.00275 \, S_h t^{-1}##
"Such equations have not been used much in mixed forests, but Mendoza and Gumpal (1987) predicted yield of dipterocarps in the Philippines with an empirical function of initial basal area, site quality and time since logging, where ##V_t## is timber yield (##m^3 ha^{-1} , 15+ cm \; dbh##), ##t## years after logging (##t>0##), ##G_0## is residual basal area (##m^2 ha^{-1}##) of dipterocarps (##15+ cm \; dbh##) after logging, and ##S_h## is site quality (##m##) estimated as the average total height of residual dipterocarp trees (##50–80 cm## diameter)."
[Modelling forest growth and yield : applications to mixed tropical forests; Jerome K. Vanclay; Southern Cross University; 1994]
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sophiecentaur said:
Not really. Yes, I know what you mean, but it's not the way I or any maths text would write it. It would be:
##3p + 2q##
The spaces are important and indicate that I have two terms added together. I wouldn't go so far as to say that 3p+2q is wrong, but it's not something I would ever write.
In general, I would tend to agree with the ISO standard on mathematical symbols:
http://www.ise.ncsu.edu/jwilson/files/mathsigns.pdf
This, I believe, is closer to what most professional mathematicians naurally would adhere to. There is no mention of PEMDAS or order of operations there.
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micromass said:
I refer you also to the ISO standard, which makes the quadratic expression quite clear without the need for PEMDAS.
There is no more need to ignore spaces in a line of mathematics than a line of text.
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PeroK said:
?? You're proposing to replace PEMDA's by "spaces"?? Come on...
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PeroK said:
I personally don't know any professional mathematician who has even heard of this particular ISO standard, sorry. All of them has heard of PEMDA's though...
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Seriously, I have read many books on sound mathematical writing. None of them says to use "spaces" instead of PEMDA's. That most professional mathematicians prefer "spaces" is just wrong.
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micromass said:
I never said they had. I said that if you look at maths publications they naturally follow the standard. A case of the standard describing how things are done, rather than the standard coming first.
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micromass said:
Then why did you put spaces in your quadratic expression?
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PeroK said:
I have read hundreds of math publications and I have never seen what you describe.
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PeroK said:
I didn't. LaTeX did it.