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# 48÷2(9+3) = ? watch

• View Poll Results: 48/2(9+3)
2
117
52.47%
288
106
47.53%

1. (Original post by Scribblet)
Type -3^2 on your calculator.
If it's similar to most of the calculators I've ever owned it will come up with -9. As we all know this isn't right.
That is right. -3^2 = -9

HOWEVER (-3)^2 = 9

The brackets actually matter hugely here.

This is because in BIDMAS, indicies come before multiplication (of the negative and the 3^2) and so the 3 must be raised to the power THEN multiplied by -1.
2. (Original post by Scribblet)
Type -3^2 on your calculator.
If it's similar to most of the calculators I've ever owned it will come up with -9. As we all know this isn't right.
Actually, it is right. You're effectively using BIDMAS/BIMDAS (whichever one you use, it doesn't matter) to raise 3 to the power of 2, and then multiplying it by -1. Therefore, brackets around (3^2) are implied, and really, the expression is:

-(3^2)
3. (Original post by andrewmc96)
I know but I cant find any other credible sources that explicitly state that "multiplication and division are on the same level and are worked from left to right".
That's because BIDMAS is a tool taught to secondary school students that becomes more or less redundant when you start doing more advanced maths, so anyone 'credible' enough to write about it just doesn't bother. It's used for people who are presented with an expression and need to bang some numbers into a calculator. It's not used so that people can write down confusing trails of numbers with operations stuck between them and then that be unambiguous -- it just doesn't work like that. Writing something like 18÷6÷3 is just bad maths, and so is writing 48÷2(9+3); whether you want to create a multitude of arbitrary rules to decide what they mean or not is besides the point, whoever writes things like this has an intended meaning, but the intended meaning isn't clear from the notation.

And this is the cause of the whole debate. People can't see beyond their own interpretation of what these things mean, so you have a "2 crew" and a "288 crew", each adamant that they're correct, each calling the other side idiots... when the truth is, ultimately, that both 'crews' are just numbed by their own ignorance.

Not that any of this really matters. I'm just surprised by how passionate people can get about thinking they're right.

EDIT: FWIW, if a 2nd year undergrad maths student counts as a credible source, hear it from me: multiplication and division are treated with equal weighting, and "left-to-right" isn't a rule (because in unambiguous statements it makes no difference). In fact you should see division as "multiplication by a reciprocal" and subtraction as "addition by a negation".
4. Im afraid your all getting it wrong.

Its quite simple to identify the error ur all making but i will leave it to u guys to figure out...
5. (Original post by nuodai)
That's because BIDMAS is a tool taught to secondary school students that becomes more or less redundant when you start doing more advanced maths, so anyone 'credible' enough to write about it just doesn't bother. It's used for people who are presented with an expression and need to bang some numbers into a calculator. It's not used so that people can write down confusing trails of numbers with operations stuck between them and then that be unambiguous -- it just doesn't work like that. Writing something like 18÷6÷3 is just bad maths, and so is writing 48÷2(9+3); whether you want to create a multitude of arbitrary rules to decide what they mean or not is besides the point, whoever writes things like this has an intended meaning, but the intended meaning isn't clear from the notation.

And this is the cause of the whole debate. People can't see beyond their own interpretation of what these things mean, so you have a "2 crew" and a "288 crew", each adamant that they're correct, each calling the other side idiots... when the truth is, ultimately, that both 'crews' are just numbed by their own ignorance.

Not that any of this really matters. I'm just surprised by how passionate people can get about thinking they're right.

EDIT: FWIW, if a 2nd year undergrad maths student counts as a credible source, hear it from me: multiplication and division are treated with equal weighting, and "left-to-right" isn't a rule (because in unambiguous statements it makes no difference). In fact you should see division as "multiplication by a reciprocal" and subtraction as "addition by a negation".
I think you've just hit the nail on the head.
6. (Original post by ada1023)
I understand what it looks like, im just applying bodmas to determine whether it looks like this:
48
---- (9+3) = 288
2

or this:
48
-------- = 2
2(9+3)

If applying bodmas, you get the first as the multiplication (the only multiplication is with (9+3)) to come AFTER the division of 48/2, and since the division is allready done with, it simply becomes 24 x 12.

Determining whether it's the first or second goes into **** which i clearly don't understand.
Forget bodmas it was never designed for such a complex piece of work roflmao, it was made for junior kids and low set high school kids, where the questions were much simpler, this is a highly complicated mathematical question which requires a whole forum to work out, i get where ur gettin the 24 x 12 but realy when it says 48 ÷ 2(9+3) then u have to see if u wna use ur bodmas idea then u can only use it with the 2(9+3) the 48 is a additional bit, think of it as a sentence, full stops are where a new sentence starts and here the full stop can be the ÷ which significes that what ever you get from doing ur bodmas bit u must divide it by 48.

seriously guys that are using bodmas your all using it wrong =/ use it on the 2(9+3) and then divide by 48, u cant use bodmas on a single number =/
7. noo
its so easy...

ill tell u what ur doing wrong after 1hour
8. I have discovered a truly remarkable proof, for the answer being 4, which this box is too small to contain.
9. keh ive given my good ideas which were right now to see if this is like a riddle i will attempt to crack it with my genious ( if i spelt genious right)

right... the question iss 48÷2(9+3) = ?

so we must start by rearanging the damn thing

48÷2(9+3) = ?

48= ?2(9+3)

48
---- =2(9+3)
?

hmm now things get complicated

48
------ = 2
?(9+3)

48
------ = 2
?(12)

48
------ = 2
12?

multiply by ?

48
------ = 2?
12

48 divided by 12 is 4

4 = 2?

4 ÷ 2 =?

2=?

wow i just worked out what the ? is equal to and its freaking 2

now we can substitude this crap in for testing, so it should equal, (idk what it should equal =/)

48÷2(9+3) = 2

48 =2(2(9+3))
48= 2(24)
48=48
1=1
omggggggggggggggggggggggg what have i doneeeeeee lol, hey i think i done aight apart from the after bold bits which may be of importance to someone smart, but yeh there you go the answer is 2, ? = 2 and that was using rearangements lol
10. Its 288 using the laws of BIDMAS or BODMAS, work out the brackets then multiply by 48/2.

EDIT then again reading the question again it looks like 48 /2(9+3).. which would = 2.

hmm
11. When you follow BIDMAS (which you always do in maths) you get:
48/2(9+3) = 288

if it was 48/(2(9+3)) then it would = 2

it all depends on how the question was originally written.
12. (Original post by krish.x)
BODMAS (Or BIDMAS) works in groups as highlighted. Brackets first, then Order/Indices, then Divide OR multiply (they are the same type of operation simply inversely proportional thus for example it doesn't matter if you do (8x2)/4 or (8/4)x2) and then Add or Subtract... Just thought I'd put that out there
I'd rather stick with D before M, if it aint broke, don't fix it. What answer did you get?
13. (Original post by King-Panther)
I'd rather stick with D before M, if it aint broke, don't fix it. What answer did you get?
Just saying. It's not DMAS its (DM)(AS) lol...

2...
14. (Original post by nuodai)
This has nothing to do with the distributive law. I could argue that we distribute multiplication by 48÷2 over the (9+3) bracket, in a similar way that you argued that only the 2 is distributed. There is no "law" which says that you have to distribute only what comes after the ÷ sign rather than the whole lot. It is ambiguous notation in that it's not clear whether the 9+3 is meant to be on the numerator or denominator of the fraction. This whole thing probably started because someone wrote this on some forum somewhere completely innocently when they meant one or the other of 2 or 288 and then someone misinterpreted it. Assuming this to be the case 42÷2(9+3) is equal to whatever the person who originally wrote it meant for it to mean. [Unless it was invented just for the sake of having a debate about order of operations, in which case the answer is simply that it's ambiguous.]

I mean, the intended value is more likely to be 2, but that doesn't mean that it is 2. The reason I say this is that if the 9+3 were meant to be on the numerator there are a multitude of other ways of writing it to make it at least a bit more obvious (even putting a * after the 2 would probably do). Also, if I were on here and saw someone write, say, 1+x/3+x I would assume it meant (1+x)/(3+x).

Also, this (because I can't be bothered typing it out again).

I wish people would stop with the whole "it's definitely {insert 2 or 288 here} and everything else is wrong; look at these rules I just made up to support my case".
I wish I had more rep, cos this would get stacks of positive.

(Original post by nuodai)
That's because BIDMAS is a tool taught to secondary school students that becomes more or less redundant when you start doing more advanced maths, so anyone 'credible' enough to write about it just doesn't bother. It's used for people who are presented with an expression and need to bang some numbers into a calculator. It's not used so that people can write down confusing trails of numbers with operations stuck between them and then that be unambiguous -- it just doesn't work like that. Writing something like 18÷6÷3 is just bad maths, and so is writing 48÷2(9+3); whether you want to create a multitude of arbitrary rules to decide what they mean or not is besides the point, whoever writes things like this has an intended meaning, but the intended meaning isn't clear from the notation.

And this is the cause of the whole debate. People can't see beyond their own interpretation of what these things mean, so you have a "2 crew" and a "288 crew", each adamant that they're correct, each calling the other side idiots... when the truth is, ultimately, that both 'crews' are just numbed by their own ignorance.

Not that any of this really matters. I'm just surprised by how passionate people can get about thinking they're right.

EDIT: FWIW, if a 2nd year undergrad maths student counts as a credible source, hear it from me: multiplication and division are treated with equal weighting, and "left-to-right" isn't a rule (because in unambiguous statements it makes no difference). In fact you should see division as "multiplication by a reciprocal" and subtraction as "addition by a negation".
This too.

As well as the guy with the Fermat reference. WIN!
15. This debate has made me lose quite a lot of faith in how maths is taught in school...
16. DO you not go by bomdas?
Brackets
Orders
Multiply
Division
Addition
Subtraction.

Tadaaaa.2 And I got a C at higher :P
17. (Original post by 786-90)
Im afraid your all getting it wrong.

Its quite simple to identify the error ur all making but i will leave it to u guys to figure out...
Enlighten us O mighty mathematical great one.
18. (Original post by lyrical_lie)
DO you not go by bomdas?
Brackets
Orders
Multiply
Division
Addition
Subtraction.

Tadaaaa.2 And I got a C at higher :P
I WISH people would stop quoting BODMAS as if it's the end of everything. If the statement does not make itself clear (as this one doesn't, along with many other similarly "unBODMAS"-able ones, such as the '18/6/3' ones already quoted), the only thing to do is ask the author for clarification.
19. (Original post by Circadian_Rhythm)
Enlighten us O mighty mathematical great one.
dont make me happy...
joking lol

its so simple man...
just read QUESTION carefully!

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