Poll: 6÷2(1+2)

lunarwolf · 29 Apr 2011 at 18:06

=1 simple, parenthesis is linked to 2 otherwise would be written => 6/2 * (1+2) or 6(1+2)/2 for it to equal 9

some need to go back to school

PS number of people who answered 9 probably explains why UK is ranked so low in education compared to other countries in EU

dowie · 29 Apr 2011 at 18:09

lunarwolf said:
=1 simple, parenthesis is linked to 2 otherwise would be written => 6/2 * (1+2)

nooooooo

adding a '*' makes no difference

FoxEye · 29 Apr 2011 at 18:11

I find it depressing how many people don't know what brackets do...

They aren't "stuck" to anything outside them. They don't elevate the priority of whatever is closest to them.

They simply mean "resolve what's inside the brackets first" and nothing else.

sk82jack · 29 Apr 2011 at 18:11

dowie said:
Dr Math has dealt with a similar problem:

http://mathforum.org/library/drmath/view/57222.html

A teacher gave a question like this as a homework assignment? What a horrible man/woman!!!

Rroff said:
Thats the problem, as it stands the equation is junk, there is no answer. Its possible to correct it to a standard for the notation format which comes out as 9, there is no standard to correct it to a version that comes out as 1 as an equation written in the format used - you need to insert an extra pair of brackets that aren't indicated in the original at all - so you might as well just add in any random operator if your gonna do that and make whatever of it you want.

I like this explanation. This helped me understand your points a lot more and I agree with the first sentence of Rroff's post, that the question is a load of rubbish, but I still don't agree there is a correct answer because we aren't computers, we have the ability to think logically and apply the most logic interpretation.

FoxEye · 29 Apr 2011 at 18:14

lunarwolf said:
=1 simple, parenthesis is linked to 2 otherwise would be written => 6/2 * (1+2) or 6(1+2)/2 for it to equal 9

some need to go back to school

Irony!

6(1+2)/2 == 6/2(1+2)

In the same way that

a/bc == ac/b

They are equal.

lunarwolf · 29 Apr 2011 at 18:17

FoxEye said:
Irony!

6(1+2)/2 == 6/2(1+2)

In the same way that

a/bc == ac/b

They are equal.

it's a/b(x+y) not a(x+y)/b

FoxEye · 29 Apr 2011 at 18:19

lunarwolf said:
it's a/b(x+y) not a(x+y)/b

Those are the same!

a/b(x+y) == a(x+y)/b

ordinaryjoe · 29 Apr 2011 at 18:21

There is an answer. It's 9. Maths has rules. Learn them

sk82jack · 29 Apr 2011 at 18:21

FoxEye said:
Those are the same!

a/b(x+y) == a(x+y)/b

only if you assume that

a/b(x+y) == (a/b)(x+y)

Not if you assume

a/b(x+y) == a/(b(x+y))

lunarwolf · 29 Apr 2011 at 18:22

FoxEye said:
Those are the same!

a/b(x+y) == a(x+y)/b

no they arent. b modifies what is in the bracket not a/b; otherwise you would need to write it (a/b)(x+y)

ie:

a
______
b(x+y)

ordinaryjoe · 29 Apr 2011 at 18:23

sk82jack said:
Yeah the '÷' symbol is never used in higher education maths and personally I think it should be removed from the education system as it confuses things (evidently lol)

So the problem is converting it to 'real life' maths and to do that you HAVE to make an assumption of where brackets should be, so there is no right answer, just an assumed right answer.

Just because some people are confused, that doesn't make it wrong - it just means that people don't know how to use it. The '÷' symbol is real maths, even if it isn't commonly used. It means the same as / would - just that when you use a / like a _____ the brackets can be implied. However, when using ÷, you assume that there are no brackets unless if you can see them.

FoxEye · 29 Apr 2011 at 18:24

lunarwolf said:
no they arent. b modifies what is in the bracket not a/b

ie:

a
______
b(x+y)

'Fraid you're wrong there mate. What's in the brackets is a separate entity and isn't "modified" by anything outside it in any special, out-of-order way.

FoxEye · 29 Apr 2011 at 18:26

sk82jack said:
only if you assume that

a/b(x+y) == (a/b)(x+y)

Which is correct.

http://mathforum.org/library/drmath/view/57222.html

Really good explanation in that link (thanks dowie).

wmb · 29 Apr 2011 at 18:26

vonhelmet said:
I've done some coding in my time, and I do lots of Excel work day to day. I'd always use brackets to make things clear to myself and to others, not least because it's considerably easier to read than if you have to interpret it using bidmas every time.

This.

Who would code a function as 1/xy when you meant y/x, which is where the ambiguity comes from in the original question. If I saw an equation as 1/xy I would assume that the brackets are missing from it and it should be 1/(xy) even if it is meant to be y/x, for the simple reason the notation is not clear.

sk82jack · 29 Apr 2011 at 18:27

ordinaryjoe said:
Just because some people are confused, that doesn't make it wrong - it just means that people don't know how to use it. The '÷' symbol is real maths, even if it isn't commonly used. It means the same as / would - just that when you use a / like a _____ the brackets can be implied. However, when using ÷, you assume that there are no brackets unless if you can see them.

No. The '÷' symbol should never be used because it creates confusion between what you want in the denominator and what you want in the numerator, clearly shown by the question in topic.

If it wasn't there and from the start people were taught to use fractions rather than '÷' then there wouldn't be half as much confusion.

Rroff · 29 Apr 2011 at 18:28

dowie said:
Dr Math has dealt with a similar problem:

http://mathforum.org/library/drmath/view/57222.html

Yeah the problem is the use of ÷ isn't correct for the format, you can either correct it for the format with / or reject it as incorrect - so the answer is either 9 or 0

ordinaryjoe · 29 Apr 2011 at 18:30

sk82jack said:
No. The '÷' symbol should never be used because it creates confusion between what you want in the denominator and what you want in the numerator, clearly shown by the question in topic.

If it wasn't there and from the start people were taught to use fractions rather than '÷' then there wouldn't be half as much confusion.

But, the problem is that people don't know how to do operators in the right order - not that it's too difficult to use the '÷' symbol.

FoxEye · 29 Apr 2011 at 18:31

ordinaryjoe said:
But, the problem is that people don't know how to do operators in the right order - not that it's too difficult to use the '÷' symbol.

Right. The problem is user error nothing more. Implying brackets where none exist, and not knowing what order to do things in without them.

sk82jack · 29 Apr 2011 at 18:32

ordinaryjoe said:
But, the problem is that people don't know how to do operators in the right order - not that it's too difficult to use the '÷' symbol.

But if there was no '÷' symbol then there wouldn't need to be a correct order, there would just be a numerator divided by a denominator.

gambitt · 29 Apr 2011 at 18:35

FoxEye said:
Read the following sentence:

"Start at the left and finish at the right."

Did you:

a) read "start" first
b) read "finish" first
c) read "pancake" over and over

I didn't ask how I asked why. Show me the axiom which states we must "start at the left and finish at the right". Or did you just make that up/remember it from primary school?

Poll: 6÷2(1+2)

6/2(1+2) = ?

9

1