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Solve this equation > 48÷2(9+3) = ?


View Poll Results: Which is right?
2 663 55.76%
288 526 44.24%
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Old 09-04-2011, 15:35
AlphaK
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deleted - duplicate post
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Old 09-04-2011, 15:39
VioletSummers
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I have. What's inside the brackets is 9 + 3 which is 12.

No. I don't know where you're getting that from but it isn't right. There is no such rule.
If you had 48/2x(9+3) I could understand why you would calculate it as you had, but the lack of multiplication sign next to the bracket means that the 2 is affixed to it and therefore should be timsed before the 48 even comes into it because of BODMAS.
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Old 09-04-2011, 15:40
5th Horseman
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which would give

48 ÷ 2*9 + 2*3 = neither 288 or 2
But that's still short form is the sum:

a) 2

48
---
18 + 6

or

b) 8.66 (recurring)

48
--- + 6
18

Of course I would go with b but unless written in long form it still leaves some potential ambiguity.
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Old 09-04-2011, 15:40
danleto
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It's 288.
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Old 09-04-2011, 15:47
AlphaK
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But that's still short form is the sum:

a) 2

48
---
18 + 6

or

b) 8.66 (recurring)

48
--- + 6
18

Of course I would go with b but unless written in long form it still leaves some potential ambiguity.
I was just messing as I believe the answer is 2
Although as I wrote it there could be a third version

48
--- *9 + 2*3 = 24 * 9 + 2*3 = 216 + 6 = 222
2
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Old 09-04-2011, 15:48
Keiō Line
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no its "2". for the reasons outlined by other posters.
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Old 09-04-2011, 15:51
*weeschmoo*
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No No!!

I keep looking at this thread and I know every time I come in it'll still be:

It's 2

no it's 288

I just can't stand it!! I want to know what the right answer is.. Stamps feet.

can we not just ask the person who made all these things up? For some reason this is driving me nuts.
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Old 09-04-2011, 15:51
Rowdy
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Maybe older posters who were taught in school to do it from left to right are getting 288, whereas those younger like myself, who were taught the bodmas method are getting 2?
Well, I'm an older poster by any measure and I get 2. Looking at it, the 2 is adjacent to the bracketed value, so it goes with it.

How would those who get 288 do this:

48÷2(x+y) ?

Or this:

48 divided by 2(9+3) (which is what it says, verbatim, in the OP)?

To rationalise to 288, it would read (48÷2)(9+3).
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Old 09-04-2011, 15:52
John259
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the lack of multiplication sign next to the bracket means that the 2 is affixed to it and therefore should be timsed before the 48 even comes into it because of BODMAS.
No, sorry but you are wrong about that. BODMAS does not say that.

BODMAS says calculate what is inside brackets first. Then powers. Then division and multiplication equally working left to right. Finally addition and subtraction equally working left to right.

2(9+3) is calculated in exactly the same way as 2 x (9+3) in every sense. Whether the multiplication sign is there or not has absolutely no effect. It is very poor notation to omit the multiplication sign when using a number before the bracket but it doesn't change how it should be calculated.
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Old 09-04-2011, 16:07
VioletSummers
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To the above poster, I'm going to try something

So we've established that it varies by opinion, but what is 48÷2x(9+3)? Does your answer change?
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Old 09-04-2011, 16:12
EllieG
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debate still underway ... seems calculators can come up with different views too!!
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Old 09-04-2011, 16:14
supanova619
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Did this in school for GCSE's and I'm currently redoing this with Open Uni for maths degree.

Writing it like this:2(9+3) is a short hand version of writing it like this: (2x9)+(2x3). Putting the 2 immediately next to the brackets is algebraic short hand for multiplying the contents of the brackets by the 2. It does not mean whack a multiplication sign in there and then work it out.

The ONLY way to get 288 is if there was a multiplication sign after the 2 which there isn't .

Those who think this is wrong, the solution is quite simple - put the equation into a scientific calculator verbatim and the answer is 2. End of story.
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Old 09-04-2011, 16:14
munta
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Ok - can I change camp - I no long say it is 288. In the strictest alegbraic sense.

x=48/2n
n=(9+3)

Therefore x=48/24
x=2

However, back in the real world, pretty much all software would assume the answer to be 288. Since I write applications to report numbers for a living I have to go with 288 for the real world.

Therefore the answer is either, depending if you deal in abstract or if you deal in reality.

Can we have this third option added to the poll
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Old 09-04-2011, 16:14
sophia93
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48÷2(9+3) - in this equation the answer is 2. You do the brackets first - getting (2x12) which is 24. 48/24 is 2.

(48÷2)(9+3) - in this equation the answer is 288. You do the brackets first and so get 24 x 12=288.
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Old 09-04-2011, 16:14
VioletSummers
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Did this in school for GCSE's and I'm currently redoing this with Open Uni for maths degree.

Writing it like this:2(9+3) is a short hand version of writing it like this: (2x9)+(2x3). Putting the 2 immediately next to the brackets is algebraic short hand for multiplying the contents of the brackets by the 2. It does not mean whack a multiplication sign in there and then work it out.

The ONLY way to get 288 is if there was a multiplication sign after the 2 which there isn't .

Those who think this is wrong, the solution is quite simple - put the equation into a scientific calculator verbatim and the answer is 2. End of story.
This this this!
Much better than how I tried to explain it.
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Old 09-04-2011, 16:15
AlphaK
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To the above poster, I'm going to try something

So we've established that it varies by opinion, but what is 48÷2x(9+3)? Does your answer change?
It does as far as I am concerned 48÷2(9+3) = 2

and 48÷2x(9+3) = 288
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Old 09-04-2011, 16:16
munta
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Did this in school for GCSE's and I'm currently redoing this with Open Uni for maths degree.

Writing it like this:2(9+3) is a short hand version of writing it like this: (2x9)+(2x3). Putting the 2 immediately next to the brackets is algebraic short hand for multiplying the contents of the brackets by the 2. It does not mean whack a multiplication sign in there and then work it out.

The ONLY way to get 288 is if there was a multiplication sign after the 2 which there isn't .

Those who think this is wrong, the solution is quite simple - put the equation into a scientific calculator verbatim and the answer is 2. End of story.
Actually, even scientifc calculators can come up with different answers
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Old 09-04-2011, 16:17
John259
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To the above poster, I'm going to try something

So we've established that it varies by opinion, but what is 48÷2x(9+3)? Does your answer change?
There is no "opinion" on this amongst mathematicians. There is one unambgious standard and that gives a result of 288.

48÷2x(9+3)
=48÷2x12
=24x12
=288

Whether the multiplication sign is present, or absent and implied by juxtaposition, has absolutely no effect, ever.
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Old 09-04-2011, 16:19
MaxbutnotMad
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if it's (48÷2)(9+3) its 288

if it's 48÷2(9+3) it's 2

THE answer is 42

probably
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Old 09-04-2011, 16:21
VioletSummers
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It does as far as I am concerned 48÷2(9+3) = 2

and 48÷2x(9+3) = 288
You see, that's what I think - that's why I think that the lack of multiplication symbol is the significant factor here. If people work it out as if there isn't one there, they get 2, whereas if they add in the multiplication sign in their head, they'll get 288.

My theory, anyway
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Old 09-04-2011, 16:21
husted
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There is no "opinion" on this amongst mathematicians. There is one unambgious standard and that gives a result of 288.

48÷2x(9+3)
=48÷2x12
=24x12
=288

Whether the multiplication sign is present, or absent and implied by juxtaposition, has absolutely no effect, ever.
Your mistake is on the first line. Its 2 multiplied by 9 AND 2 muliplied by 3.

Always do the sum inside the Brackets first. BODMAS.
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Old 09-04-2011, 16:21
kingofcakes
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This makes my head hurt.
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Old 09-04-2011, 16:23
supanova619
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OMFG!!!

The very fact that there is no sign between the 2 and the brackets means that the 2 belongs to the brackets.

People need to realise that BODMAS/BIDMAS is not the only mathematical theory going on here. There is also algebra to think of.

EDIT (less confusing explanation)

There is no multiplication sign to be put between the 2 and the brackets. 2(9+3) does not mean 2 x (9+3). It means (2x9)+(2x3). Anyone who has successfully studied algebra will know this.
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Old 09-04-2011, 16:25
AlphaK
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Ok - can I change camp - I no long say it is 288. In the strictest alegbraic sense.

x=48/2n
n=(9+3)

Therefore x=48/24
x=2
Using substitution into an algebraic expression appears to give a different answer to using actual values because the ambiguity is removed.

Edited to add - appears to give
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Old 09-04-2011, 16:31
husted
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OMFG!!!

The whole reason the multiplication sign is there is because it comes immediately before the bracket. The very fact that there is no sign between the 2 and the brackets means that the 2 belongs to the brackets.

People need to realise that BODMAS/BIDMAS is not the only mathematical theory going on here. There is also algebra to think of.
There is no algebra here. Algebra is the concept of variables representing numbers. If there was an 'x' there it would be:

2x(9+3) = 18x + 6x = 24x.

When you are evaluating an expression, BODMAS is the convention even in algebra. Brackets first.

All you have is a multiplication symbol:

2x(9+3) = 2(9+3) = 18+6 = 24.

Brackets first. Always.
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