48÷2(9+3)

Gaigemasta · **Joined:** Dec 2006 **Posts:** 4474 **Location:**

Gaigemasta wrote:

I think this thread needs to be locked

Tasdik · **Joined:** Jan 2007 **Posts:** 13206 **Location:** Life

Uhh, so I'm friends with the best mathematician in my state, he says the answer is 2.

His opinion > Yours.

[SD]Master_Wong · **Posted:** Sun Apr 10, 2011 8:26 pm

iv spent a few hours looking around asking questions the answer is 2, not because of what anyone has said here but because the mnemonics are misleading, addition and subtraction are of the same level of importance as is multiplication and division not only that iv got too many people who have studied math swearing blind the answer is 2

3:24 onwards

.curve · **Posted:** Sun Apr 10, 2011 8:39 pm

Shit just got serious. wtf is happening right now.

Mark. · **Joined:** Mar 2008 **Posts:** 672 **Location:** Italy

[SD]Master_Wong wrote:

iv spent a few hours looking around asking questions the answer is 2, not because of what anyone has said here but because the mnemonics are misleading, addition and subtraction are of the same level of importance as is multiplication and division not only that iv got too many people who have studied math swearing blind the answer is 2

3:24 onwards

Doesn't that only apply where there are Xs and such?

I mean...5(2x+1) is obviously 10x + 5, but if we suppose that x=2, then we can have 5(4+1)=25 or 5(5)+5(1)=25, so it doesn't really matter whether you do the brackets first or not.

EvGa · **Joined:** Apr 2008 **Posts:** 2612 **Location:** Texas

Tasdik wrote:

Uhh, so I'm friends with the best mathematician in my state, he says the answer is 2.

Can you have him work it out? I'm serious.

Masterwong, you are correct, this was mentioned earlier in the thread... same level of importance from left to right.

48/2(9+3) <=Brackets
48/2(12)

48/2(12) <=Multiply/Divide LEFT to RIGHT
24(12)

24(12) <= Multiply/Divide Left to Right
288

Tasdik · **Joined:** Jan 2007 **Posts:** 13206 **Location:** Life

He looked at it again, this is what he said.

Quote:

Strictly speaking, you would have to put parenthesis around the whole denominator to divide by the whole thing => giving you 2.

I was wrong. Sad day.

EvGa · **Joined:** Apr 2008 **Posts:** 2612 **Location:** Texas

Yeah, in academia and/or research you would never encounter a math problem structured like this.

Kirkaldi · **Joined:** Jul 2008 **Posts:** 3083 **Location:** nyc

someone lock this thread. its 288. if anyone still thinks its 2, go get a math tutor NOW

[SD]Master_Wong · **Posted:** Sun Apr 10, 2011 10:35 pm

i cba to argue my point seeing as what i thought was right turns out wrong and i argued the 288 point for most of this thread

just look it up, or find someone who studied math beyond school is all im going to say to everyone

EvGa · **Joined:** Apr 2008 **Posts:** 2612 **Location:** Texas

[SD]Master_Wong wrote:

i cba to argue my point seeing as what i thought was right turns out wrong and i argued the 288 point for most of this thread

just look it up, or find someone who studied math beyond school is all im going to say to everyone

Beyond school? Like, at the college level? Does calculus I and II count? Linear algebra? Plane geometry, discrete structures, probability & statistics count? lol...

[SD]Master_Wong · **Posted:** Sun Apr 10, 2011 10:49 pm

EvGa wrote:

[SD]Master_Wong wrote:

i cba to argue my point seeing as what i thought was right turns out wrong and i argued the 288 point for most of this thread

just look it up, or find someone who studied math beyond school is all im going to say to everyone

Beyond school? Like, at the college level? Does calculus I and II count? Linear algebra? Plane geometry, discrete structures, probability & statistics count? lol...

guess so but im with most people where i was taught to see it was 288, but people i know one who scored nearly 100% in every math test says different the other is a computer engineer he says the same neither are stupid so given it appears to be a simple question would they get it wrong

honestly i was good at math but i pushed myself at the wrong times so ended up best in my class in the intermediate rather then the hard paper in school so wasnt taught this back then, i didnt go on to do A level math either 3 people who i asked did and all 3 said 2 also some random dude from work

so after a bit of explaining from one of them im changing my answer as it makes sense, 2( is attached to the brackets as Amarisa said so its done first and not because of bidmas but because of some other reason which i cba to go get the term for it from my mate forgot what he called it but nether the less im sticking with my answer now right or wrong

Azilius · **Joined:** Oct 2006 **Posts:** 4236 **Location:** CS:GO

Amarisa wrote:

VeniVidiVici wrote:

Get the brackets away gives: 48/2(9+3) = 48/(18+6) = 48/24 = 2

Edit: Damn after rewatching it I'm hesitating now. Because it could also mean:
48/2(9+3) = 48/2*12 and that would mean 288.

48÷2(9+3) ≠ 48÷2*1(9+3)

The number infront of the parentheses is attached to the parentheses by distributive law.

If you have a plain old (9+3) it is the same as 1(9+3). How ever 2(9+3) the 2 takes the one spot and becomes attached to it by distributive law.

That being said 2(9+3) = (2 * 1(9 + 3))

so 48÷(2*1(9+3))

It states that 48 is divided by 2 and because the 2 is attached to the (9+3) it becomes 48 over 2(9+3).

Umm no.

Simple way to prove you wrong..

-(1)^2 and (-1)^2

First one yields -1, second one yields 1. Brackets come first, and according to you the term right outside the brackets that doesn't have a star symbol denoting it's multiplication must be evaluated first. Not sure why you think that. But if you do follow that logic you'd get

-(1)^2 => (-1)^2 = 1
when in reality
-(1)^2 => -(1*1) => -(1) = -1

@ evga
just did taylor/maclauren series as well, fun stuff :sohappy:

Shomari · **Joined:** Jul 2007 **Posts:** 2341 **Location:** Limbo

48/2(9+3)
-
48/2(12)
-
48 * 1/2(12)
-
48 * 6
-
288

I probably did something wrong.

.curve · **Posted:** Sun Apr 10, 2011 11:58 pm

EvGa wrote:

Masterwong, you are correct, this was mentioned earlier in the thread... same level of importance from left to right.

See, this was my confusion. I swear I was taught that MDAS were to be done in that order. MD and AS on the same level of importance, just done left to right makes sense though.

I learned something derp derp.

EvGa · **Joined:** Apr 2008 **Posts:** 2612 **Location:** Texas

Azilius wrote:

@ evga
just did taylor/maclauren series as well, fun stuff :sohappy:

Shweet. They are not as bad as a lot of people make them seem, just messy. I'm waiting on my test score to come back form a test over series we took Thursday. :giveup:

Wong, distributive property maybe?

[SD]Master_Wong · **Posted:** Mon Apr 11, 2011 12:52 am

EvGa wrote:

Azilius wrote:

@ evga
just did taylor/maclauren series as well, fun stuff :sohappy:

Shweet. They are not as bad as a lot of people make them seem, just messy. I'm waiting on my test score to come back form a test over series we took Thursday. :giveup:

Wong, distributive property maybe?

one said SI, but for the life of me i cant work out what SI is, iv heard of distributive property somewhere not sure if it was here or a mate

Quote:

the answer is 2 if you're using SI. which is the true way of reading equations. you would read it as 48/(2 x (9+3))

Quote:

They teach different at a-level... you're relying on basic stuff they teach to kids to make it easy rather then the proper way of doing it which is why google gets it wrong.

Hapjap · **Posted:** Mon Apr 11, 2011 1:02 am

TIL

internetz wrote:

The distributive property of multiplication CLEARLY states that the 2(9+3) is an entire statement and CANNOT be broken up. 2(9+3) follows the distributive property which can be rewritten as (2*9+2*3). Let me repeat the 2 outside of the parenthesis follows the distributive property of multiplication and must be factored and simplified before performing any other operations on it. You do NOT compute this expression from left to right until you use Algebra to simplify the statement 2(9+3).

So this can be rewritten as:
48 / (2*9 + 2*3)

Which leaves us with

48 / 24 = 2

Hmm. seems now that both can be right. if you interpret 2(9+3) as 2*(9+3), its 288. apparently 2(9+3)=/= 2*(9+3) so, you don't compute the expression from left to right first, because the 2(9+3) actually simplifies to (2*9 + 2*3), so you compute that first, making the answer 2.

EDIT: So apparently, some calculators will even give you the wrong answer. When you enter 2(9+3), it automatically assumes 2*(9+3), and doesn't take into consideration distributive property.

internetz wrote:

Google and some calculators do not understand many theorems or properties so you must explicitly explain what you mean. There is a difference between 48 / 2 * (9+3) and 48 / 2(9+3). The first notation reads 48 / 2 * 1(9+3) while the second reads 48 / (2*9+2*3). Be very careful with your signs.

heroo · **Joined:** Sep 2006 **Posts:** 6618 **Location:**

i failed.

/thread

Amarisa · **Joined:** Feb 2008 **Posts:** 4049 **Location:** Magic

Quote:

guess so but im with most people where i was taught to see it was 288, but people i know one who scored nearly 100% in every math test says different the other is a computer engineer he says the same neither are stupid so given it appears to be a simple question would they get it wrong

Well I might not compare to the person you know that scored 100% on most math tests. But I do score pretty darn high on my math tests without doing homework/studying.

Quote:

honestly i was good at math but i pushed myself at the wrong times so ended up best in my class in the intermediate rather then the hard paper in school so wasnt taught this back then, i didnt go on to do A level math either 3 people who i asked did and all 3 said 2 also some random dude from work

I kinda was in those "slow" classes because I never did homework. It was always too easy for me so I never bothered to do homeork. It wasn't until middle of High School did they begin to notice I got A's and B's on tests yet I didn't do an ounce of homework. Infact most of the time I get a problem wrong is because I accidently changed a number or something of the sort.

Quote:

so after a bit of explaining from one of them im changing my answer as it makes sense, 2( is attached to the brackets as Amarisa said so its done first and not because of bidmas but because of some other reason which i cba to go get the term for it from my mate forgot what he called it but nether the less im sticking with my answer now right or wrong

I am no math expert as I can't explain it all too well. I am only in plain old college algebra and we are right now going over i and that fun junk. Though I kinda went over that last year of high school.

[SD]Master_Wong · **Posted:** Mon Apr 11, 2011 1:43 am

Amarisa wrote:

Quote:

honestly i was good at math but i pushed myself at the wrong times so ended up best in my class in the intermediate rather then the hard paper in school so wasnt taught this back then, i didnt go on to do A level math either 3 people who i asked did and all 3 said 2 also some random dude from work

I kinda was in those "slow" classes because I never did homework. It was always too easy for me so I never bothered to do homeork. It wasn't until middle of High School did they begin to notice I got A's and B's on tests yet I didn't do an ounce of homework. Infact most of the time I get a problem wrong is because I accidently changed a number or something of the sort.

lol one teacher miss wheeler she expected me to fail i got a pathetically low predicted score, i hated how she treated me, i never tried in mock tests couldnt be arsed but come the proper one i was the 2nd highest in the class on that paper tier and about 4th highest in the year on that tier all in all suck it bitch

Amarisa · **Joined:** Feb 2008 **Posts:** 4049 **Location:** Magic

[SD]Master_Wong wrote:

Amarisa wrote:

Quote:

honestly i was good at math but i pushed myself at the wrong times so ended up best in my class in the intermediate rather then the hard paper in school so wasnt taught this back then, i didnt go on to do A level math either 3 people who i asked did and all 3 said 2 also some random dude from work

I kinda was in those "slow" classes because I never did homework. It was always too easy for me so I never bothered to do homeork. It wasn't until middle of High School did they begin to notice I got A's and B's on tests yet I didn't do an ounce of homework. Infact most of the time I get a problem wrong is because I accidently changed a number or something of the sort.

lol one teacher miss wheeler she expected me to fail i got a pathetically low predicted score, i hated how she treated me, i never tried in mock tests couldnt be arsed but come the proper one i was the 2nd highest in the class on that paper tier and about 4th highest in the year on that tier all in all suck it bitch

Yea most teachers thought I had ADD my parents were about to put me on a prescription until one just plain out said I was just stubborn. I don't know why but like 90% of the things I learn in school I classify as "easy." Maybe I am just a fast learner or something.

Maybe I don't push myself enough and I could be in a much more advanced class then I am now.

Azilius · **Joined:** Oct 2006 **Posts:** 4236 **Location:** CS:GO

Hapjap wrote:

EDIT: So apparently, some calculators will even give you the wrong answer. When you enter 2(9+3), it automatically assumes 2*(9+3), and doesn't take into consideration distributive property.

internetz wrote:

Google and some calculators do not understand many theorems or properties so you must explicitly explain what you mean. There is a difference between 48 / 2 * (9+3) and 48 / 2(9+3). The first notation reads 48 / 2 * 1(9+3) while the second reads 48 / (2*9+2*3). Be very careful with your signs.

That's wrong.

I followed a nice 40 page thread on another forum where someone linked images to his casio calculator giving the answer as 2 when he didn't use the * symbol, only 2(9+3). Later someone linked an article released by casio where they admitted there was an issue with older calculator models not following proper order of operations (the aforementioned issue) and it has since been fixed.

tldr
a*b = a(b)
Refer to -(1)^2 example, or the fact that casio fixed their own issue

Mirosuke · **Posted:** Mon Apr 11, 2011 2:43 am

THIS... IS.... SRF OFFTOPIC LOUNGE. :sohappy:

YangKang · **Joined:** Dec 2006 **Posts:** 838 **Location:**

strong misc presence/10

penfold1992 · **Joined:** Apr 2007 **Posts:** 4060 **Location:**

i just did it again and i got 286 which is weird because thats 288-2... how did i get that?
using a different method of some complex long division and calculus i also managed to get -2+288i and -2-288i....

Amarisa · **Joined:** Feb 2008 **Posts:** 4049 **Location:** Magic

penfold1992 wrote:

i just did it again and i got 286 which is weird because thats 288-2... how did i get that?
using a different method of some complex long division and calculus i also managed to get -2+288i and -2-288i....

as long as you don't divide by 0 we should be ok.

The Invisible · **Joined:** Jan 2011 **Posts:** 2626 **Location:** Home ._.

penfold1992 wrote:

i just did it again and i got 286 which is weird because thats 288-2... how did i get that?
using a different method of some complex long division and calculus i also managed to get -2+288i and -2-288i....

That's because you use complex long division while it is a simple equation .

Why not simply admit that you it is solved with 1 way only and i wonder why don't you just use a calculator and that calculator that solved it wrong must be pretty old .

What do you guys need to as proof to admit that it is 288 not 2 ?

Well i tried Casio ( Calculator ) and it said the answer is 288 .

CeLL · **Posted:** Mon Apr 11, 2011 1:21 pm

Braingeyser wrote:

The problem lies in the way the equation was written, leading many to interpret it in more than one way. Equations should be unambiguous, and clearly represent the problem it questions. Based solely on the order of operations the answer should be 288 and not 2. However, writing the number 2 juxtaposed to a parenthesis (without the multiplication operator) tricks some to think the whole thing is a denominator [ referring to 2(9+3) ] which is how some people are used to writing equations (especially on a single line).

tldr;
if you answered 2 after seeing 48/2(9+3)
you're not wrong, but the equation is.

yes, they are wrong. its not 2. this shit doesnt take a genious. i cant believe this is still being discussed.

The Invisible · **Joined:** Jan 2011 **Posts:** 2626 **Location:** Home ._.

48/2(9+3) = 48/2*(9+3) .

So in both ways it is 288 .

and if anyone solved it wrong then he didn't follow the right rules to answer this equation type .

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