BODMAS or PEMDAS
03-25-2015, 03:01 AM
Post: #1
 lloydc61 Junior Member Posts: 2 Joined: Mar 2015
BODMAS or PEMDAS
Hello,

Was hoping someone could clarify if this is a known fault, or am I overlooking something. Recently someone posted on LinkedIn the following brain teaser 6÷2(1+2)= stating that 9 out of 10 people get this wrong.

Well it seems that even the HP Prime cannot decide which is the correct way to solve. If I enter as written whilst in "Algebraic" entry mode I get 9 as the answer. But if I then use "Textbook" entry mode I get 1 as the answer. This seems to fall into the great debate as to whether you use BODMAS or PEMDAS.

Lloyd
03-25-2015, 06:00 AM
Post: #2
 Gerald H Senior Member Posts: 1,429 Joined: May 2014
RE: BODMAS or PEMDAS
(03-25-2015 03:01 AM)lloydc61 Wrote:  Hello,

Was hoping someone could clarify if this is a known fault, or am I overlooking something. Recently someone posted on LinkedIn the following brain teaser 6÷2(1+2)= stating that 9 out of 10 people get this wrong.

Well it seems that even the HP Prime cannot decide which is the correct way to solve. If I enter as written whilst in "Algebraic" entry mode I get 9 as the answer. But if I then use "Textbook" entry mode I get 1 as the answer. This seems to fall into the great debate as to whether you use BODMAS or PEMDAS.

Lloyd

Yes, the great debate.

6 2 / 1 2 + *

or

6 2 1 2 + * /

Works like magic.
03-25-2015, 06:22 AM
Post: #3
 Han Senior Member Posts: 1,810 Joined: Dec 2013
RE: BODMAS or PEMDAS
(03-25-2015 03:01 AM)lloydc61 Wrote:  Well it seems that even the HP Prime cannot decide which is the correct way to solve. If I enter as written whilst in "Algebraic" entry mode I get 9 as the answer. But if I then use "Textbook" entry mode I get 1 as the answer. This seems to fall into the great debate as to whether you use BODMAS or PEMDAS.

BODMAS vs PEMDAS ... I'm not sure I see any distinction other than using synonyms. [B]rackets are [p]arentheses, and [o]rders are [e]xponents. DM vs MD ... there's no difference, esp. if you think of division as being multiplication of inverse (would would be [e]xponent/[o]rder of (-1) followed by multiplication -- I suppose that would also be a [p]arentheses/[b]racket first if we want to be really technical about division)

As for algebraic mode vs textbook mode... shouldn't they behave differently (just like RPN behaving differently from either)? Otherwise they'd just be the same mode, right? Moreover, they're entry modes, not an implementation of order of operations (which is actually the same for all modes, and occurs after completed entry).

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03-25-2015, 07:07 AM
Post: #4
 lloydc61 Junior Member Posts: 2 Joined: Mar 2015
RE: BODMAS or PEMDAS
(03-25-2015 06:22 AM)Han Wrote:
(03-25-2015 03:01 AM)lloydc61 Wrote:  Well it seems that even the HP Prime cannot decide which is the correct way to solve. If I enter as written whilst in "Algebraic" entry mode I get 9 as the answer. But if I then use "Textbook" entry mode I get 1 as the answer. This seems to fall into the great debate as to whether you use BODMAS or PEMDAS.

BODMAS vs PEMDAS ... I'm not sure I see any distinction other than using synonyms. [B]rackets are [p]arentheses, and [o]rders are [e]xponents. DM vs MD ... there's no difference, esp. if you think of division as being multiplication of inverse (would would be [e]xponent/[o]rder of (-1) followed by multiplication -- I suppose that would also be a [p]arentheses/[b]racket first if we want to be really technical about division)

As for algebraic mode vs textbook mode... shouldn't they behave differently (just like RPN behaving differently from either)? Otherwise they'd just be the same mode, right? Moreover, they're entry modes, not an implementation of order of operations (which is actually the same for all modes, and occurs after completed entry).

Yes, that is my point, the two modes are just entry differences in the way the equation is shown, the end result should be the same I would have thought.
03-25-2015, 11:26 AM
Post: #5
 DrD Senior Member Posts: 1,101 Joined: Feb 2014
RE: BODMAS or PEMDAS
(03-25-2015 03:01 AM)lloydc61 Wrote:  Hello,

6÷2(1+2)= stating that 9 out of 10 people get this wrong.

Lloyd

If 6÷2(1+2) out of 6÷2(1+2)+1 people are wrong then 1 can't be right ...

(Would someone please pass the brackets.)

-Dale-
03-25-2015, 01:01 PM
Post: #6
 rprosperi Senior Member Posts: 3,818 Joined: Dec 2013
RE: BODMAS or PEMDAS
(03-25-2015 03:01 AM)lloydc61 Wrote:  But if I then use "Textbook" entry mode I get 1 as the answer.

I get 9 using Textbook, with and without the implied multiplication. What are you entering?

--Bob Prosperi
03-25-2015, 03:20 PM
Post: #7
 Han Senior Member Posts: 1,810 Joined: Dec 2013
RE: BODMAS or PEMDAS
(03-25-2015 07:07 AM)lloydc61 Wrote:  Yes, that is my point, the two modes are just entry differences in the way the equation is shown, the end result should be the same I would have thought.

Your interpretation of "entry differences" is that the same key presses are displayed different but should yield the same result. That is not (and should not be) correct. The correct interpretation is that they are different entry modes so that you would have to enter your input differently in order to get the same results using a different entry mode. For example, in RPN mode I cannot press the keys [2] [+] [3] in that order and have it yield the same result as in algebraic mode (the former leads to an error and the latter correctly yields 5). In textbook mode, an integral (using the template) is entered very differently from algebraic mode, so trying the same sequence of keys would assuredly not give the same results (in textbook mode, if you use the template, you actually have to navigate with the arrow keys).

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