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On 2006-11-06 23:59:14, bluesun wrote:
Quote:
PS 9 is the WRONG answer
is it?!! damn. i've always thought that (1+2)*3 is 9.
unless you meant 1+(2*3), then 9 is not the correct answer.
[ This Message was edited by: bluesun on 2006-11-06 23:05 ]
Hi, you are correct in your calculations *when you add the parentheses*, however this is ruled by something known as BODMAS (Brackets Of Divide Multiply Add Subtract), so you original calculation *should* have performed the multiply *prior* to the addition.
BODMAS doesn't seem to be covered in schools so much these days
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Posted: 2006-11-07 12:24:37
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Quote:
On 2006-11-07 12:24:37, dpat wrote:
Hi, you are correct in your calculations *when you add the parentheses*, however this is ruled by something known as BODMAS (Brackets Of Divide Multiply Add Subtract), so you original calculation *should* have performed the multiply *prior* to the addition.
BODMAS doesn't seem to be covered in schools so much these days
gee. you do learn (or relearn) new things everyday. thanks for the fyi.
in that case, the calculator in my mac is also flawed.
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Posted: 2006-11-07 21:32:19
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Quote
1+2*3=7
(1+2)3=9
1+(2*3)=7
So if you type 1+2*3 so should the answer be 7
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Posted: 2006-11-07 21:36:27
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Quote
i dont really want to get into the math but i really wouldn't call the calc on my m600 flawed.
you simply have to understand how it works. its true that "1+2x3" should equal 7 but it is also easy to see that the calc on the m600 sees the input as (1+2)x3 as it is performing calculations one step at a time.
i for one have no problems using this calculator.
if for example the calculator displayed the full calculation "1+2x3" and then produced the answer 9 i would be worried but as it stands it is mathematically correct.
button display
1 =1
+ =1
2 =2
x =3
3 =3
= =9
Also the fact that "x" should be performed before "+" is a convention rather than a mathematcal rule.
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Posted: 2006-11-08 03:06:46
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Quote
@mobman
Good point, it can potentially be confusing for beginners to use scientific calculators that handle priorities correctly. There is however a visual clue since these calculators *don't* display "3" when you have pressed 1+2*. Typically it looks like this:
button display
1 1
+ 1
2 2
* 2
3 3
= 7
Thus, these calculators keep the "2" when you have pressed the "*", indicating that the previous operator "+" has not yet been evaluated.
The calculator I made take this one step further and displays the stack of unevaluated expressions, which you can see in the screenshot below.
The top (small) display line shows the current expression stack, while the bottom display line shows the current input or output.
As for conventions: mathematics is full of conventions that we all accept, such as the meaning of "1" and "+". The convention of priorities just happens to be less known among non-scientists.
If you are used to deal with mathematic texts, it is really a pain to use a calculator that does not handle priorities. That's why I made my own calculator.
Note that MS Windows builtin calculator has two modes: standard and scientific. In standard mode, 1+2*3 is evaluated to 9, while in scientific mode it is evaluated to 7.
Niclas
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Posted: 2006-11-08 08:55:28
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