Solve this simple math problem: 48/2(9+3)

[alvindarkness]

I must say i just found this sight through google and had to join because of this post. I am a math teacher and the correct answer is 2

48/2(9+3) is a different equation than 48/2 * (9+3)

using Pemdas or the correct order of operations in the first problem
we first add whats in the parentheses (9+3)= 12
second step we multiply 2(12) =24
final step 48/24 = 2

the people who are getting 288

are adding (9+3) =12
then they are skipping an order of operations and going straight to division 48/2 =24
24 * 12 = 288

Multiplication doesn't have precedence over division in the order of operations. 1÷2÷3(1+2)÷5*6÷7*9 would have the parenthesis done first.. then the rest done left to right. So the next step is 1÷2÷3*3÷5*6÷7*9

Wolfram alpha visualises both of those as the same. i.e.

http://www.wolframalpha.com/input/?i=1÷2÷3(1+2)÷5*6÷7*9

and

http://www.wolframalpha.com/input/?i=1÷2÷3*3÷5*6÷7*9

I agree that the translation of the equation into ascii can cause cause some vagueness, or at least second guessing the intent of the author (was he short handing "all over" with "/" for example). But we have to work with what we have, and I definitely see it as a 288.

 

[McGiord]

Who said that this an equation? What is the variable that is unknown?

2 is still winning!

 

[dukebound85]

In regards to calculators and OSX spotlight
http://en.wikipedia.org/wiki/Calculator_input_methods
http://en.wikipedia.org/wiki/Order_of_operations

With the immediate execution mode of operation each binary operation is executed as soon as the next operator is pressed, therefore the order of operations in a mathematical expression is not taken into account. Scientific calculators have buttons for brackets and these calculators can take order of operation in to account

Different calculators follow different orders of operations. Most non-scientific calculators without a stack work left to right without any priority given to different operators

while more sophisticated calculators will use a more standard priority

Who said that this an equation? What is the variable that is unknown?

2 is still winning!

Well it is an equation as it is the same as as saying x=48/2(9+3)

 

[McGiord]

Oh wow, your previous arguments about how "because spotlight says 2 therefore it is true no matter what" are just so convincing!

Failing with math and now failing with reading?

 

[iStudentUK]

Who said that this an equation? What is the variable that is unknown?

2 is still winning!

Means nothing. Either answer would be correct- it is ambiguous. Using "/" notation is poor practice. I believe, for the reasons I stated a few posts ago (post 146), the author would intend an interpretation leading to 288.

 

[ramzhh]

For god's sake, this is still alive? Look, there is more than one possibility. Now no one should care. Mystery solved. Now get to actual work.

Dunno why this was posted in the first place...

 

[Phil A.]

I must say i just found this sight through google and had to join because of this post. I am a math teacher and the correct answer is 2

48/2(9+3) is a different equation than 48/2 * (9+3)

using Pemdas or the correct order of operations in the first problem
we first add whats in the parentheses (9+3)= 12
second step we multiply 2(12) =24
final step 48/24 = 2

the people who are getting 288

are adding (9+3) =12
then they are skipping an order of operations and going straight to division 48/2 =24
24 * 12 = 288

Sorry, you are wrong (math teacher or not!)

48/2(9+3) is 48/2(12) (parenthesis first)
=48 divided by 2 multiplied by 12
division and multiplication have the same order of precedence so are executed left to right

that means 48 divided by 2 = 24 multiplied by 12 = 288

To get 2 requires you to make assumptions about the equation. If you make no assumptions and simply apply the rules then you get 288

 

[iStudentUK]

To get 2 requires you to make assumptions about the equation. If you make no assumptions and simply apply the rules then you get 288

No matter what you do you have to make an assumption as to what "/" means. Nobody over the age of 10 should be using that notation for this exact reason.

Therefore, assume that author wanted to use "_" but couldn't as this is a forum not suited to equation writing and work from there. I believe the logical conclusion is 288, but that is not the same as saying the answer is 288.

 

[McGiord]

Well it is an equation as it is the same as as saying x=48/2(9+3)

Well the OP said it is an equation. Guys you are failing the reading questions also.

Now if we said it is like stated by dukebound85.

What will the value of X in order to obtain 48 on the right side of the equation, please take your time and move all the numbers to the left side of the equation.

Have fun.

 

[ender land]

using Pemdas or the correct order of operations in the first problem
we first add whats in the parentheses (9+3)= 12
second step we multiply 2(12) =24
final step 48/24 = 2

the people who are getting 288

are adding (9+3) =12
then they are skipping an order of operations and going straight to division 48/2 =24
24 * 12 = 288

Does division come after multiplication in order of operations? I had always thought you treated both multiplication and division the same and executed those operations sequentially, reading left to right.

I'm calling BS on you being a math teacher.

McGiord - "Mac OS X cannot be wrong on this: [refering to picture showing 2 as answer]." Perhaps you do not remember saying this? What about "Mac OS X cannot be wrong"? I know reading your posts results in fail, but associating that fail with someone else failing at reading is a bit of a stretch.

And for what it's worth, I guess I am quite happy if my current position is "failing at math" considering I make a fair bit of money for "failing at math" in a technical field.

 

[McGiord]

For god's sake, this is still alive? Look, there is more than one possibility. Now no one should care. Mystery solved. Now get to actual work.

Dunno why this was posted in the first place...

Yes it is, and continually showing us that the right answer is 2.

I care.

I do not work today.

 

[alvindarkness]

Who said that this an equation? What is the variable that is unknown?

2 is still winning!

You don't need a variable for it to be an equation.

Definition of Equation - An equation is a mathematical statement that asserts the equality of two expressions. Equations consist of the expressions that have to be equal on opposite sides of an equal sign.

Definition of Expression - In mathematics, an expression is a finite combination of symbols that are well-formed according to the rules applicable in the context at hand. Symbols can designate values (constants), variables, operations, relations, or can constitute punctuation or other syntactic entities.

 

[McGiord]

You don't need a variable for it to be an equation.

Definition of Equation - An equation is a mathematical statement that asserts the equality of two expressions. Equations consist of the expressions that have to be equal on opposite sides of an equal sign.

Definition of Expression - In mathematics, an expression is a finite combination of symbols that are well-formed according to the rules applicable in the context at hand. Symbols can designate values (constants), variables, operations, relations, or can constitute punctuation or other syntactic entities.

Great use of the Dictionary.
Like the right answer to the OP question, I asked 2 questions:
The right answer to the first one is: the OP said it was an equation.
The right answer for the second question I made is: _______________ (fill in the blank space).

 

[notjustjay]

And for what it's worth, I guess I am quite happy if my current position is "failing at math" considering I make a fair bit of money for "failing at math" in a technical field.

Yep. As long as we're throwing credentials around let me get out my two electrical engineering degrees.

It's 288.

If my degrees don't convince you, maybe this will:

http://en.wikipedia.org/wiki/Order_of_operations
http://mathcentral.uregina.ca/QQ/database/QQ.09.07/h/brit1.html
http://www.onlinemathlearning.com/bedmas.html
http://www.mathsisfun.com/operation-order-pemdas.html
http://www.mathsisfun.com/operation-order-bodmas.html
http://math.about.com/library/weekly/aa040502a.htm
http://bctf.ca/diversity/ResourceInventory/LessonsTopics/Davies/BEDMAS.pdf
http://www.purplemath.com/modules/orderops.htm
... and plenty more where those came from.

Notice that "multiplication and division" always appear together as a step, as in one does NOT take precedence over another, but they are expressed left to right. They do NOT say to do the multiplication part (2x12) before the division (48/2)!

Therefore it's 48/2(9+3)
Which becomes 48/2(12) [brackets]
Which implies 48/2*12
Which is 24*12
Which is 288.

 

[McGiord]

Kids continue having fun...time to file my taxes.

And I do expect my return to be accurate like the right answer.

 

[ender land]

Yes it is, and continually showing me that the right answer is 2 in spite of all evidence to the contrary.

Fixed that for you.

 

[Rodimus Prime]

I must say i just found this sight through google and had to join because of this post. I am a math teacher and the correct answer is 2

48/2(9+3) is a different equation than 48/2 * (9+3)

using Pemdas or the correct order of operations in the first problem
we first add whats in the parentheses (9+3)= 12
second step we multiply 2(12) =24
final step 48/24 = 2

the people who are getting 288

are adding (9+3) =12
then they are skipping an order of operations and going straight to division 48/2 =24
24 * 12 = 288

I feel sorry for your students because you are teaching them incorrect things

No matter what you do you have to make an assumption as to what "/" means. Nobody over the age of 10 should be using that notation for this exact reason.

Therefore, assume that author wanted to use "_" but couldn't as this is a forum not suited to equation writing and work from there. I believe the logical conclusion is 288, but that is not the same as saying the answer is 288.

umm what the hell are you talking bout. / means divide plan and simple. No assumption are being made.
In higher level class you go dot see that - with dots above and below it in anything more than maybe text books and even then it is not that common.

Reason for it is the / is much clearer and less likely to be interpreted another operation (subtraction) by mistake. the / is very clear.
honestly I can not think of the last time I used something other than the / for division. I might of been in Jr high so close to 15 years ago. I know I sure as hell never used anything but the / in my upper level math class (cal and beyond)

 

[iStudentUK]

umm what the hell are you talking bout. / means divide plan and simple. No assumption are being made.
In higher level class you go dot see that - with dots above and below it in anything more than maybe text books and even then it is not that common.

/ is not clear, how far does the division extend? Exactly as we see here. Using _ is much more clear. The best notation would be ( ... )^-1

People can talk about PEDMAS, order of operations etc but that is kiddies stuff really. Nobody ever used / during my chemistry degree, none of my tutors or lecturers spent time talking through PEDMAS and the like. Using _ or to the power of -1 is much clearer. It's even more confusing if you use / when there is another division in the denominator.

EDIT- I'm not talking about ÷, I'm talking about using / or _

 

[TuffLuffJimmy]

umm what the hell are you talking bout. / means divide plan and simple. No assumption are being made.
In higher level class you go dot see that - with dots above and below it in anything more than maybe text books and even then it is not that common.

Reason for it is the / is much clearer and less likely to be interpreted another operation (subtraction) by mistake. the / is very clear.
honestly I can not think of the last time I used something other than the / for division. I might of been in Jr high so close to 15 years ago. I know I sure as hell never used anything but the / in my upper level math class (cal and beyond)

Or when you reach an actually high math class you simply express division as a fraction.

 

[Phil A.]

/ is not clear, how far does the division extend?

That's like saying how far does the multiplication symbol extend if used in an equation: It's a mathematical symbol synonymous with ÷ and extends to the next number (or parenthesised statement)

You wouldn't think that 4 x 5 + 4 meant 4 x (5 + 4), so why would you think that 48 / 2 x 12 meant 48 / (2 x 12)?

 

[AppleMacFinder]

The official Mac answer is: 2

We are at MacRumors! Finder says 2, that's why we should accept 2.

 

[iStudentUK]

You wouldn't think that 4 x 5 + 4 meant 4 x (5 + 4), so why would you think that 48 / 2 x 12 meant 48 / (2 x 12)?

I don't think a typical mathematician would write this on paper using a "/", rather they would use a "_". Using / on anything more complex than x/y is very poor form.

Here, I assume / is being used as MacRumors isn't set up for writing equations. So I asked myself how would I write this in _ format?

I thought the answer would be-

48 (9 + 3)
2

Hence leading to 288.

The problem is / leads to confusion because you don't know if the person typing wanted to use a _ but couldn't, it is the intention and use that is confusing, not the symbol itself. Nobody should have to use PEDMAS for something silly like this- people should write equations in a decent format.

EDIT- using the x symbol is also something I don't like to do if I can avoid it. 5x6 or 5*6 not as good as 5(6) (or just xy if algebra is involved).

 

[AndrewR23]

Hmm I get 288 learning the way I was taught while in school.


Although my math professor at UC IRVINE said Pemdas is wrong.

 

[paolo-]

I don't think a typical mathematician would write this on paper using a "/", rather they would use a "_". Using / on anything more complex than x/y is very poor form.

Here, I assume / is being used as MacRumors isn't set up for writing equations. So I asked myself how would I write this in _ format?

I thought the answer would be-

48 (9 + 3)
2

Hence leading to 288.

The problem is / leads to confusion because you don't know if the person typing wanted to use a _ but couldn't, it is the intention and use that is confusing, not the symbol itself. Nobody should have to use PEDMAS for something silly like this- people should write equations in a decent format.

EDIT- using the x symbol is also something I don't like to do if I can avoid it. 5x6 or 5*6 not as good as 5(6) (or just xy if algebra is involved).

Agreed. Anyhow, writing math with ascii characters sucks, however you put. Most people who aren't used to see math in ascii see / as a ______ and not as a direct translation of ÷ or (...)^-1. Other than the people who blindly follow PEMDAS and think multiplication has a precedence over division, like our lovely math teacher did a couple posts above, I think the poll would tend a lot more towards 288 if the question was posted with TeX (or another proper form).

I think this poll has more to do with how bad math can be written in plain characters than it has to do with the average person's understanding of math. Hey, I got it right, but I spend a lot of time using math and do see it a lot in plain characters, but I know most people aren't engineering students.

 

[McGiord]

Agreed. Anyhow, writing math with ascii characters sucks, however you put. Most people who aren't used to see math in ascii see / as a ______ and not as a direct translation of ÷ or (...)^-1. Other than the people who blindly follow PEMDAS and think multiplication has a precedence over division, like our lovely math teacher did a couple posts above, I think the poll would tend a lot more towards 288 if the question was posted with TeX (or another proper form).

I think this poll has more to do with how bad math can be written in plain characters than it has to do with the average person's understanding of math. Hey, I got it right, but I spend a lot of time using math and do see it a lot in plain characters, but I know most people aren't engineering students.

Well Paolo, what is your answer?