Math Hurts: 48÷2(9+3)

[DGiant2000]

Guys, the PEDMAS/BIDMAS/BODMAS/BEDMAS/'whatever else'MAS argument is really invalid. It does not really work, as I said and Famine reiterrated, DM and AS have equal weighting. It's a gimmick to get people through their GCSE or equivalent. As I said before, a calculator knows BODMAS and for this reason will get the square (or indeed any even power) of a negative number wrong, it is flawed. The simple answer really is that it's badly written Maths. The 2(9+3) is correct without an operator though, the multiplication is assumed, algebra or numbers aside.

 

[DriverD00d]

Odd...That just made sense. 💡
I guess my teacher didnt know what she was teaching...She stated that you multiply when A number is before brackets

 

[diabolicwyvern]

I see, you do all the 'right side' math and move to the left?

You must satisfy Order of Operations.

EDIT: My grade school math teachers were all liars.

 

[Omnis]

Why is this 7 pages long?

 

[SohnVonStig]

Why is this 7 pages long?

A very good question. More perplexing than the one the thread itself proposes IMO.

 

[DGiant2000]

You must satisfy Order of Operations

No you really don't, unless you're doing your GCSE's, there are so many things you are taught which you then have to re-learn, that's what really frustrates me with some of the Maths teaching in this country (and obviously yours too)

 

[lbsf1]

No you really don't, unless you're doing your GCSE's, there are so many things you are taught which you then have to re-learn, that's what really frustrates me with some of the Maths teaching in this country (and obviously yours too)

Well said, in my Gcse maths there is so much stuff that contradicts stuff you have learnt before.

I think the problem is that there isn't enough questions in context, for example when in life would you solve a question using bodmas, if it was in context in a question like you get in life then you can use more logic rather than just remembering your maths lesson.


/gcse maths rant.

 

[Ibonibo]

 

[Azuremen]

.4x

If you want 2/(5x), then write it with the parens.

Why??!?!?! It's AFTER the division when worked left to right!!! There's no other grouping symbol used to override the left-to-right order.

You would be in the minority reading it that way, at least in a sciences/engineering/mathematics group. Famine very clearly explained the reasoning why.

And left to right is something I don't think anyone actually thinks about once you really start doing calculus; I know I sure as hell haven't thought about it. I throw it in the box with the mnemonics - devices designed to make it easier to perform operations, but necessarily correct. Which applies to many, many "rules" like I before E except after C and so on.

Odd...That just made sense. 💡
I guess my teacher didnt know what she was teaching...She stated that you multiply when A number is before brackets

That is what he did. The issue is how implied multiplication is understood by most people.

Also, you could just apply the distributive rule to the 2 and get 48/(18+6)

ibo racer, I think you troll face image is backwards, just saying.

 

[Omnis]

The top way is wrong. If you separate them like that, it becomes (48/2) * (1/(9+3))

Follow the AUP and don't knowingly post wrong stuff.

 

[diabolicwyvern]

No you really don't, unless you're doing your GCSE's, there are so many things you are taught which you then have to re-learn, that's what really frustrates me with some of the Maths teaching in this country (and obviously yours too)

GCSE --Could you please write out in english for those of us not in the know.

 

[DGiant2000]

GCSE --Could you please write out in english for those of us not in the know.

Sorry, GCSE - General Certificate of Secondary Education - is your final exam at secondary school for students aged 16. I think it's the same as your finals at high school but I could be wrong as I'm not overly familiar with your education system.

 

[Ibonibo]

The top way is wrong. If you separate them like that, it becomes (48/2) * (1/(9+3))

Follow the AUP and don't knowingly post wrong stuff.

Sorry but it is 48/2 * (9+3)
=24 * 12

As it is stated several times, there is a difference in how I, we / you, you learnt it.
And as it is written badly the 2 different learning methods collide.

In fact as you state the AUP: The question can be used to fuel an argument because it plays with the 2 different learning methods by having a mathematicly badly written equation

 

[DGiant2000]

Sorry but it is 48/2 * (9+3)
=24 * 12

Based on what?

 

[Azuremen]

Sorry but it is 48/2 * (9+3)
=24 * 12

As it is stated several times, there is a difference in how I, we / you, you learnt it.
And as it is written badly the 2 different learning methods collide.

In fact as you state the AUP: The question can be used to fuel an argument because it plays with the 2 different learning methods by having a mathematicly badly written equation

What you are ignoring is what some highly educated members have said about this, including Famine, who was educated under the same method. I'd recommend you read his post if you haven't.

 

[Ibonibo]

How we learn it here.
It doesn't matter if you write it
48/2

or

48
----
2

That's the same thing

 

[arora]

Based on what?

The troll logic pic of course, found here.

http://knowyourmeme.com/memes/48293

 

[DGiant2000]

How we learn it here.
It doesn't matter if you write it
48/2

or

48
----
2

That's the same thing

Ok, well without sounding condescending, I have a degree in Maths, A post graduate certificate in secondary education in Maths and 10 years experience in teaching Maths. Therefore I have learnt 'a lot of Maths' and I can assure you that whilst the sum is written ambiguously, any mathematician would read the answer as 2 unless the 48/2 was put into brackets.

 

[Rossticles]

 

[salanos]

Either way I see it, it works out to 2...

 

[wfooshee]

I've not seen the orders as are being used here. I was always taught that multiplication and division carry equal weight, you just do them as encountered left to right.

As for the parens, once you'e added 9 and 3, you have 2 times 12, but the times is to the right of the divide, so my teaching says divide first.

I've NEVER been taught anywhere that multiplication came before dicision, or that addition came before subtraction. I was taught Parens, exponents, mult/div (equal weight), then add/sub (equal weight). By that, the answer is 288.

If you do multiplication before division, then it's 2. But I wouldn't do that if I encountered the problem as it's written. My answer would be 288. As I might have said before.

I've never heard 2(9+3) expressed as lots, nor heard of a rule putting such lots before other operations.

 

[itsbenjibrand]

I'll ask my math teacher this question tomorrow. We'll see what the answer is.

 

[Azuremen]

I've never heard 2(9+3) expressed as lots, nor heard of a rule putting such lots before other operations.

Like I've said, it is more common in higher level math to do the implied multiplication first, thus 2/5x would be read as 2/(5x). Very, very view people would even consider 0.4x as the result. Famine has explained this very, very clearly.

I'll ask my math teacher this question tomorrow. We'll see what the answer is.

Oh look.

Ok, well without sounding condescending, I have a degree in Maths, A post graduate certificate in secondary education in Maths and 10 years experience in teaching Maths. Therefore I have learnt 'a lot of Maths' and I can assure you that whilst the sum is written ambiguously, any mathematician would read the answer as 2 unless the 48/2 was put into brackets.

 

[arora]

Based on how much this has spread I'm guessing school teachers are cursing the internet about now

(48÷2)(9+3)=288

48÷[2(9+3)]=2

48÷2(9+3) =

I've been waiting to see this ..........

 

[dylansan]

Like I've said, it is more common in higher level math to do the implied multiplication first, thus 2/5x would be read as 2/(5x). Very, very view people would even consider 0.4x as the result. Famine has explained this very, very clearly.

This. Very much this.

Just because a calculator doesn't group the 2 and the 9+3 together, it doesn't make it right.

2/5x = 2/(5*x)

2/5*x = (2*x)/5

Implied multiplication > Order of operations

 

[Dravonic]

(48÷2)(9+3)=288

48÷[2(9+3)]=2

48÷2(9+3) =

This, exactly this. There's no point in arguing it. The equation is written ambiguously on purpose, with the intent of tolling. After this many pages, you can tell it succeeded.

 

[WeinerSchnitzel]

288. First try.

 

[G.T]

When I first saw it, from my initial workings out, I would have got 288, but I understand how people say it's 2. The original layout is pretty ambiguous so I can see why there's a confusion.

 

[salanos]

If you ask me I'd follow that while there is typically a left-to-right rule, I would deal with things between signs first, which is why I can't really see this coming to 288, but only 2...

 

[wfooshee]

Like I've said, it is more common in higher level math to do the implied multiplication first, thus 2/5x would be read as 2/(5x).

Well, like I've said, it's not what I was taught, although that would probably be a bit before when you were taught. In my '70's world there is no difference between 2/5x and 2/5*x. Theres no such thing a implied multiplication, the 5x is 5*x. Doing it without the * does not make it a higher priority.

Also, like I said, in my '70s world, multiplication was not done before division, it was equal weight left to right.

As for "higher" math, I was an engineering student at Auburn University. I've had some exposure . . . . But it was a while back.

I accept that if the rules have changed since the Dark Ages, or if the rules are different in different countries or even different parts of the same country, then the answer could be 2. But not where I came from.

(One of the things you find with "old" people is that they're stubborn!)