Calculator Order of Operations

[jason4570]

Question: depending on the calculator I get different answers. If I try 1+2*3... both calculators give me the correct answer of 7, thus meaning according to websites, they follow the order of operations.

However this problem... 2(8) -:- 4(2).... gives me two different answers. The graphing calculator that can recognize paretheses as multiplication give me an answer of 2.... 2(8) = 16... 4(2) = 8... then divides. But this appears out of order? I can type it how I see it... 2(8) -:- 4(2) Is there some unwritten rule like when typing in negative numbers raised to a power in a graphung calculator... that you MUST use parentheses... -9^2 = -81... thus you have to type (-9)^2 to get a correct answer of 81

The other older non graphing calculator works the problem... 2(8) = 16 then divides 4 = 4 then multiplies 2 = 8. But I have to type it "2 x 8 -:- 4 x 2 ="

Order of operations seems to work. Is the graphing calculator wrong? Should I type it in differently? Or is it correct and I'm doing the order of operations incorrectly?

Please assist.

P.S. I am using -:- as division because the divide is not the bar or forward slash in the original problem... it's the line, two dot division.

 

[jason4570]

2 * 8 / 4 * 2 = 8
2 * 8 / (4 * 2) = 2
Over and out!

Which is correct... there are no other parentheses other than (8) and (2)

Order of operations... Mult/Div. L => R... you do 2x8-:-4x2 = 8. This answer works on non-graphics or calculators that don't recognize parentheses as multiplication... thus you have to manually type in the 'X' times... button.

Again the graphics calculator... many of them... TI/Casio/online... if you type "2(8) -:- 4(2)" it will tell you the answer is "2", which appears incorrect as far as the order of operations goes.

Are the calculators wrong... or is it operator error of not knowing how to key punch the actual problem in correctly.

 

[stapel]

Different calculators and different spreadsheets (and other technology) evaluate the expression differently, due to the ambiguity of the formatting. There are two different interpretations of it, which led to the two different values you obtained.

FYI: Every time I've seen this type of question come up, the discussion quickly degenerates into a slug-fest, with the population fairly evenly divided between the two camps. Do NOT expect to get "the" answer here or anywhere (because there is, as yet, no "the" answer to give).

Apologies in advance for what's very likely shortly to start erupting.

 

[Bob Brown MSEE]

\(\displaystyle \frac{2*8}{4*2}


\text{ = 2*8/(4*2)
}
\)

\(\displaystyle \frac{2*8}{4*2}


\text{ = 2*8/4/2
}
\)
Are both generally accepted.


\(\displaystyle \frac{2*8}{4*2}


\text{ = 2*8 / 4*2
}
\)
Is not generally accepted.
I have seen attempts to use spaces as parenthesis, but you should use parenthesis if you have any doubt.

 

[jason4570]

Thank you everyone for the responses. I do appreciate it.

The "ambiguity" of the question a fine "answer". There are other in math cases of ambiguity where there are two/multiple answers but those are logical and can be explained.

This one we could not think of a logical reason why besides maybe operator error... it was hard to phathom calculators being programed wrong. Thus why I was asked.

Thanks again.