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# 48÷2(9+3) = ? watch

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

1. (Original post by DanielleT192)
The questioner doesn't expect you to use a calculator to work out this question or have a "computing minded" mode, but use initiative to what you could see.

I don't think so. This is nothing to do with computers, The problem, as written, is perfectly solvable using ordinary rules of maths - the "trick" in the wquestion (and perhaps the point of the question) is that you have to remember to insert the implied operator between the 2 and the "(9+3)". The correct answer, mathematically, is 288.
2. (Original post by wanderlust.xx)

So... if my teachers weren't lying... the answer is 2 and 288.
You have just invented a branch of maths that uses simultaneous, parallel, operators.

With BIDMAS it's assumed you divide, although at school I was told that both division and multiplication are interchangeable; that is, it doesn't matter which one comes first (the same apparently goes for +/-)
When the priorities are the same you go from left to right.
3. (Original post by HistoryRepeating)
Are you, and every other idiot in this thread claiming anything other than 2, trolling?

Seriously, are you all really that stupid?

The reason you are getting it wrong is you are treating these two equations as the same, when they are not:
48/2(9+3)
48/2x(9+3)

In the latter, the correct answer is 288.

In the former, the correct answer is 2.

In the former, the 2 is a multiplicand and therefore dealt with prior to the /

BIDMAS is too basic for these problems.
To achieve the answer 2 though, you have to place a set of parentheses around the 2(9+3) part, otherwise you wouldn't prioritise multiplying those two things before dividing 48 by the result. That would change the equation.

The order goes:

48/2(9+3)
48/2(12)

Since you're only left with multiplication and division, and these two hold equal importance, you just work from left to right to get: 48/2 = 24 * 12 = 288.
4. I believe the answer is 2
5. I believe the answer is 2 too.
6. I'm pretty sure I'd put the answer is 2. Since in BODMAS you do the brackets first, and the 2 is touching the brackets with no sign in between, I would consider applying the two (ie. 2 x 12) a part of simplifying the brackets, so the answer's two. If it was (48÷2)(9+3) I'd see how it'd be 288, but otherwise
7. (Original post by DanielleT192)
But you're basically saying that 48 divided by 2(12) should be treated as 48 divided by 2 and then multiplied by 12 to obtain the answer of 288 simply because of the arrangement of BODMAS. Multiplication and division are treated equally, as does subtraction and addition and I'm guessing the only reason that BODMAS is spelt that way is to make it easier for people to remember the rule that brackets takes priority in terms of arithmetic equations.

Really, it's the way the question is set out and that is the most important thing. The questioner doesn't expect you to use a calculator to work out this question or have a "computing minded" mode, but use initiative to what you could see. So I still stick to 2, even though it's obvious the question isn't presented well.

You're definitely right here, but the standard convention is to compute from left to right when you have a series of operations. It's not that I'm prioritising multiplication over division or anything, I'm just simplifying it and working it out from left to right.
8. (Original post by theciz)
the 2 is touching the brackets with no sign inbetween, I would consider applying the two (ie. 2 x 12) a part of simplifying the brackets,
It isn't. Read my post 127.

More generally in relation to this, at what are people taught the precendece of operators these days? I'd have thought this would be a year 7 sort of topic. I'd be very worried if people doing GCSEs and above are getting it wrong.
9. This is essentially the same problem as was discussed here:

http://www.thestudentroom.co.uk/show....php?t=1524946

Some manufacturers have adopted the convention that something like 2(3) is treated as 6 whereas others treat 2(3) as 2*3.

Consequently 18/2(3) can result in 3 or 27 on different calculators.

You will find the behaviour of your calculator described in detail in its instruction book.

This has been an awful thread.

10. it's 2... basic GCSE maths is basic...
11. (Original post by Barden)

it's 2... basic GCSE maths is basic...
Have you read any of the explanations as to why it is not, and plan to counter any - or you do you intend to just be wrong?
12. It really isn't two
13. (Original post by Barden)

it's 2... basic GCSE maths is basic...
But not basic enough for some, it appears.
14. (Original post by Barden)

it's 2... basic GCSE maths is basic...
no, no, it really isn't
15. (Original post by Good bloke)
It isn't. Read my post 127.

More generally in relation to this, at what are people taught the precendece of operators these days? I'd have thought this would be a year 7 sort of topic. I'd be very worried if people doing GCSEs and above are getting it wrong.
Hah, I wouldn't even be surprised. I was no good at maths without my calculator. If only I had it now...

In all honesty though I wouldn't know the ins and outs of BODMAS. Learnt it in first year then never dealt with it explicitly again, even at A Level. Although by that stage you'd hope to have it down. Obviously I didn't.
16. (Original post by Barden)

it's 2... basic GCSE maths is basic...
It really isn't two. It really is 288. This isn't me applying "common sense", its me applying the correct rules of precedence.

BIDMAS is just a shorthand for kids. Other countries use BODMAS, or, crucially, BIMDAS or BOMDAS.

The real order of precedence goes:
terms inside brackets
exponents and roots
multiplication and division

There is no precedence between Multiplication and Division. In other countries they dont use BIDMAS they use PEMDAS (google it) for example.

There is a further rule you need to know - You apply operators of equal precedence from left to right (same goes for addition and subtraction, or exponents and routes) in any equation.

48÷2(9+3)
48÷2(12)
24(12)
288

On a similar note and using the same rules, the notation 1/2y is 0.5y not 1/(2y).

This is 100% correct, not just my opinion, its how maths notation on this point works, no question. Horribly, about half of all calculators apply this wrongly...

Edit:

Its useful to think of division as multiplication of the inverse and subtraction as addition of a negative number, following which the parse order doesnt matter

48÷2(9+3)
48x(1/2)(9+3)
288
17. (9+3) = 12; 48/2(12) = 2
18. (Original post by Good bloke)
I don't think so. This is nothing to do with computers, The problem, as written, is perfectly solvable using ordinary rules of maths - the "trick" in the wquestion (and perhaps the point of the question) is that you have to remember to insert the implied operator between the 2 and the "(9+3)". The correct answer, mathematically, is 288.
Not meaning to be rude, but is mathematics your area of study? I haven't studied maths in further education, but I don't believe it's necessary for this question.

People are saying that you should be working from left to right. Technically speaking, when you figure out the 2(12) as the brackets takes precendence, then you are still working from left to right. When I studied maths and was presented with big calculations involving brackets I'd put my priority into figuring out the numbers obtained from the brackets and then work out the calculation as a whole.
19. (Original post by Profesh)
This, surely?
You too Profesh? How embaressing.

Operators of equal precedence (multiplication and division) get parsed left to right...
20. (Original post by DanielleT192)
Not meaning to be rude, but is mathematics your area of study? I haven't studied maths in further education, but I don't believe it's necessary for this question.

People are saying that you should be working from left to right. Technically speaking, when you figure out the 2(12) as the brackets takes precendence, then you are still working from left to right. When I studied maths and was presented with big calculations involving brackets I'd put my priority into figuring out the numbers obtained from the brackets and then work out the calculation as a whole.
How nice for you, but you are wrong. You work out the INSIDE of the brackets first, then apply the usual rules (ie multiplication and division are equal precedence so parse the whole thing left to right)

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