48÷2(9+3) = ?

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multiplication with a dash? the source is me, and i believe it to be true because that's what we were told in A level maths.

Degree level maths begs to differ.

Reply 241

py0alb

Original post by HistoryRepeating

Wrong that it is irrelevent because writing it as:
48/2(9+3)
causes exactly the same debate (and is still 288)

No, there is a clear difference between

\frac{48}{2(9+3)}

and

\frac{48}{2}(9+3)

Reply 242

Good bloke

Original post by F1Addict

Confused.

Multiplication and division have equal precedence. They are therefore processed from left to right in the absence of relevant brackets. The same applies to addition and subtraction, of course.

Reply 243

byraul

it's 288!

Reply 244

$Avatar for Get me off the £\?%!^@ computer$

Get me off the £\?%!^@ computer

Original post by Good bloke

Post 192 will demonstrate to you that the calculator manufacturers don't know what day of the week it is.

The people who make the TI Nspire don't know what day of the week it is. :rofl:

Can I buy my next calculator from you please?

I can't guarantee it but I would expect that the documentation for the TI 85 and TI 86 specify exactly how they each deal with those expressions. I admit that they should make their minds up though.

Which one I prefer is my business and I'm certainly not going to bother arguing about whether the answer to this question is 2 or 288.

Reply 245

Rancorous

Think this sums up how ridiculous this forum is with most of its threads. It's basic maths - you don't get an 'opinion'. And we all have to respect other people's opinions no matter how retarded they are, because God if someone who has acquired high rep comes up with something moronically stupid and you tell them so, you're in the red.

Reply 246

F1Addict

Original post by Good bloke

Multiplication and division have equal precedence. They are therefore processed from left to right in the absence of relevant brackets. The same applies to addition and subtraction, of course.

Oh, i was never taught that way.. :tongue:

It still makes it 288 though. :smile:

Reply 247

HistoryRepeating

Original post by DanielleT192

1/2x=1/2x it'd only be 1/2 x if it were displayed like 1/2 (x)
It's the way the question is presented. I keep emphasizing this.

Thats just wrong on so many levels. Its frankly amazing that you think (x) functions different from x.

Reply 248

username133326

Original post by rmhumphries

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?

I have read them, they don't stand up to scrutiny. BIDMAS is BIDMAS.

EDIT: oh... right, now i see it :facepalm:

(edited 13 years ago)

Reply 249

DFranklin

Original post by HistoryRepeating

The rules of notation I'm describing are universal, its what mathematicians really do, and are based on university level experience. It's certainly not what I do, and it's not what I remember any lecturer ever doing, based on 4 years at Cambridge.

I'd grant you that the actual question posed is a lot greyer, but if I was supervising and had a student write 3x/2y = 3xy/2 I'd think they didn't know what they were doing.

Of course, at university level, if someone meant 3xy/2 they'd write it exactly like that. (In fact, most mathmos I know very much avoid relying on left-to-right precendence anyhow - if they meant(48/2)(9+3) they would either write it like that or 48(9+3)/2).

However textbooks dont use normal text to write equations. so it would be written like this...

I've certainly had handouts where things like 3x/2y were written. But as you say, typesetting in textbooks is better than you get on a forum, and even hardwritten work has more subtlety. But this is part of the point.

If you saw

3x/2 \, \, y

you'd be much more likely to interpret it as

3xy/2

than if you saw

3x/2y

even though the only difference is a small gap between the 2 and the y.

On a forum, you can't have such subtleties. Which is why it's not cut and dried - was there supposed to be a space in between or not? But I'd say usage on math forums is overwhelmingly that 3x/2y =

\frac{3x}{2y}

. (In fact, on forums most mathematicians will understand 1+x / 1-x to be

\frac{1+x}{1-x}

, even if they don't actually like it being written like that).

Reply 250

The Dynamic Uno

If it was 2 would the the equation not be:

48÷[2(9+3)] ?

Reply 251

Aeschylus

I've gone with the option of having a girlfriend and a life

EDIT:

This thread is like a blunt pencil

POINTLESS

(edited 13 years ago)

Reply 252

SparksInTheSky

Original post by dothat

Why have you suddenly started going from right to left?

48/2(9+3)
= 48/2(9+3)
= 24(12)
= 288

It's 2.
BIDMASS - when it says brackets it doesn't just mean 'do' the bracket it means multiply out the bracket.

therefore:
48/ 2(12)
=48/ 24
=2

Reply 253

HistoryRepeating

Original post by py0alb

No, there is a clear difference between

\frac{48}{2(9+3)}

and

\frac{48}{2}(9+3)

Thats a completely different notation.

When using vertical fractional notation, vertical position effectively functions as parentheses.

That is simply not a function of using dash. 1/2 is not the same notation as

\frac{1}{2}

Even though in this instance they give the same result.

edit: to be clearer, the equivilent notation to:

\frac{x+y}{a(b+c)}

is (x+y)/(a(b+c))

When converting from vertical fractional notation to normal text you need to add parentheses around the expressions that are offset vertically in the fractional notation for equivalence to be maintained.

So 48/2(9+3) still causes the problems outlined (and is still 288).

(edited 13 years ago)

Reply 254

Boristhethird

bodmas

Brackets
over
devision
multiplcation
addition
subtraction

so its 2 (N.B. calculators are not usually clever enough to do this, and will just work from left to right.)

Reply 255

smiffhead

Original post by HistoryRepeating

Please cite any source that states that coefficients should be considered BEFORE (division and multiplication).

PS: I'm not using BODMAS or any other mnemonic, but the actual rules of mathematical notation which are used at a university level.

Dashes are very rarely used to show multiplication! was that wikipedia by any chance?! i'm trying to find a source to back me up now. If this was 48 ÷ 2x surely more people would be answering '2'

Reply 256

Good bloke

At the time of writing the score stands 9-5 in favour of the 288s. It shows how poor democracy can be as a decision-making system when over a third of the public doesn't even nderstand year 7 maths.

Reply 257

smiffhead

Original post by HistoryRepeating

you sure? you are only 18, where you looking? or are u in first year?

Reply 258

nuodai

Original post by Good bloke

At the time of writing the score stands 9-5 in favour of the 288s. It shows how poor democracy can be as a decision-making system when over a third of the public doesn't even nderstand year 7 maths.