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Original poster

Maths Disagreement

593 replies

TulaOfDarkWater · 04/02/2022 12:41

One person thinks the answer is 165 and the other thinks 67, who is right?

YABU - 165
YANBU - 67

Or what’s the answer if both are wrong?

Maths Disagreement
OP posts:
TeenPlusCat · 05/02/2022 09:59

[quote Itsalmostanaccessory]@NumberTheory

You dont need bracket in this.
You only need them if you are NOT competent. We didnt have brackets for simple things like this in high school, nor were they added when I was at uni and working through various equations because they are not needed.[/quote]
I think Number is well aware. Smile

The point really is that unless you can really be confident that all readers of your equation are competent (ie within a STEM situation) the safer thing is to include brackets.

The original puzzle plays on people not being fully competent, and stupid 'tricks' that really are nothing to do with maths anyway.

UniversalAunt · 05/02/2022 10:12

‘ I vote for 38, but I also think 67 is a fair answer. Not everyone who needs glasses can be bothered finding them and nor should they have to.’

Fair answer? Oh dear, there are no runner up prizes in getting maths right, otherwise bridges would fall down, medicines would not be correctly dosed etc.

However that said, this is why showing your workings, in homework, exams & research, is important as everything will be correct until the method & workings go wrong, & as we all know points mean prizes.

PugInTheHouse · 05/02/2022 10:25

@TulaOfDarkWater if shapes were all the same it would be 3+4+(4x15) = 67

I think the actual answer is

2+4+(4x11)=50

2 =clock
4=bananas
11=number of sides on the shape

PugInTheHouse · 05/02/2022 10:26

Sorry my eyesight is crap, I think there are 3 bananas on the last one so

2+3+(3×11)=38

5566rfghh · 05/02/2022 10:27

@GettingStuffed

Unfortunately there's two types of maths. The stuff we did in schools years ago when you worked left to right unless there were brackets, this new maths means to do things in a particular order.

Who decided this way was better? So it's possible to be two "correct" answers depending on when you went to school.

Maths is maths!!!! This way isn't better, it's CORRECT. You're remembering wrong or else you were taught incorrectly. So no it doesn't depend on when you went to school.
bruffin · 05/02/2022 10:27

[quote PugInTheHouse]@TulaOfDarkWater if shapes were all the same it would be 3+4+(4x15) = 67

I think the actual answer is

2+4+(4x11)=50

2 =clock
4=bananas
11=number of sides on the shape[/quote]
There are only 3 bananas

NoVaxDjokovic · 05/02/2022 10:35

@GettingStuffed

Unfortunately there's two types of maths. The stuff we did in schools years ago when you worked left to right unless there were brackets, this new maths means to do things in a particular order.

Who decided this way was better? So it's possible to be two "correct" answers depending on when you went to school.

Order of operations was around in the 1800’s

So either you are the worlds oldest person (congrats) or you are wrong…

PugInTheHouse · 05/02/2022 10:35

@bruffinyes I corrected myself after, I am on my phone and they are too small for my eyes Grin

PugInTheHouse · 05/02/2022 10:37

@gettingstuffed there is definitely only one way of doing it, order of operations wasn't necessarily taught properly in schools till about the 80s however you would have been given brackets if not taught it. Do the calculation on a calculator with no brackets and it will give you the correct answer.

hivemindneeded · 05/02/2022 10:38

But @Itsalmostanaccessory, if you haven't been taught any mathematical conventions it would seem logical to progress left to right, like you do with reading. So you 2+3+3xY could be read accummulatively as 2+3=5, then take that 5 and +3=8, then x that 8 by Y. Surely you can see how many people would arrive at this method of working things out if they haven't been taught otherwise. It's what loads of people do on these sorts of brainteasers, so clearly maths teacher has failed colossally.

Translate it into real life and it's not clear whether it means make 11 sets of 2 apples, 3 pears and 3 oranges
or one set of 2 apples, 3 pears and 33 oranges.

hivemindneeded · 05/02/2022 10:40

@Gettingstuffed just isn't wrong about the teaching. She may have been taught wrongly but she (or he) like me was simply not taught BIDMAS. Doesn't matter how long it's been around. If you're not taught it, you don't automatically work it out for yourself.

Itsalmostanaccessory · 05/02/2022 10:42

@hivemindneeded

I get people think they haven't been taught it/dont remember it/some really were taught very badly by teachers who have failed.
But once it has been explained, that should be it. Look at the mess if this thread because they just wont listen.

At the start of this, they might not have known, but anyone reading it certainly should understand it now. Yet... still people post nonsense.

The inability to read and actually take it in is astounding.

TeenPlusCat · 05/02/2022 10:44

I've seen maths teachers on MN bemoaning they have classes swear blind they haven't covered something before, when the teacher knows they have because she taught it to them the previous academic year.

My guess is yes it was taught, but no it wasn't revisited sufficiently for it to become ingrained.
Much like I suspect half the English grammar now being taught at primary which then isn't built on at secondary.

ClumpingBambooIsALie · 05/02/2022 10:49

@hivemindneeded

But *@Itsalmostanaccessory*, if you haven't been taught any mathematical conventions it would seem logical to progress left to right, like you do with reading. So you 2+3+3xY could be read accummulatively as 2+3=5, then take that 5 and +3=8, then x that 8 by Y. Surely you can see how many people would arrive at this method of working things out if they haven't been taught otherwise. It's what loads of people do on these sorts of brainteasers, so clearly maths teacher has failed colossally.

Translate it into real life and it's not clear whether it means make 11 sets of 2 apples, 3 pears and 3 oranges
or one set of 2 apples, 3 pears and 33 oranges.

The mathematician would not fare so well working at a fish and chip shop, hearing "cod and chips three times please", and handing over a single piece of fish and three bags of chips.
TeenPlusCat · 05/02/2022 10:57

The mathematician would not fare so well working at a fish and chip shop, hearing "cod and chips three times please", and handing over a single piece of fish and three bags of chips.

Grin

Though when speaking spaces / commas do the work of brackets.

  • cod and chips-three-times
  • cod-and-chips three times
ClumpingBambooIsALie · 05/02/2022 10:58

I must remember to pronounce my brackets clearly Grin

TeenPlusCat · 05/02/2022 10:58

I had fun at university. A friend liked to drink 'pineapple juice and diet coke' (yes, mixed together). I always had to clarify to the bar staff.

ClumpingBambooIsALie · 05/02/2022 11:00

@TeenPlusCat

I had fun at university. A friend liked to drink 'pineapple juice and diet coke' (yes, mixed together). I always had to clarify to the bar staff.
Dear God. No wonder you had to be explicit.
MadameMachin · 05/02/2022 11:03

165

Shmithecat2 · 05/02/2022 11:08

Maths teacher in a former life. The answer is 38. 2+3+3×11.

Itsalmostanaccessory · 05/02/2022 11:13

@MadameMachin

165
See what I mean. You can't teach stupid. People are still posting this nonsense because they cant understand what has been explained or simply think they know better.
cherrybonbons · 05/02/2022 11:30

You assumed brackets for multiplication because according to BODMAS- you do the multiplication BEFORE addition

PugInTheHouse · 05/02/2022 11:38

Seriously, after 20 pages people are still saying 165. The fruit/clocks etc confuse everything. The basic maths concept is the issue.

Very rarely will people have to do a maths calculation like that if not actually studying maths so maybe it's irrelevant but what strikes me is how people are so unwilling to learn new things or relearn what they have forgotten. If you have kids or grandkids it's useful to know the correct way of doing things.

Over the years there had been many changes in education, English grammar for one, the various things taught all have different names but are essentially the same as what was taught years ago. If BODMAS wasn't taught then brackets would have been, I had never heard of half the stuff DS1 did in English but I recognised the skill rather than the name. I didn't just ignore what he was doing because I wasn't taught it.

MrsRugbyMa · 05/02/2022 11:42

It's almost impossible to see that there are 4 bananas in the second row Confused. It's a very silly task.

poetryandwine · 05/02/2022 11:45

@TeenPlusCat makes a great point that brackets are the commas of number sentences. It is really only polite to use them

Possibly most who don’t remember BODMAS did have lessons on it, but here is a true story: when I was lecturing a certain Maths course in a STEM School at a Russell Group university, a student showed me an geometry worksheet of his from a well known highly selective boys’ school

Data was given about right triangles and you had to fill in the missing data. But in many examples the data was impossible. If you remember the Pythagorean Theorem, the square of the long side of a right triangle is the sum of the squares of the other two sides. This worksheet was full of ‘right triangles’ with side lengths like 4, 5, 7 or
2, 8, 10, etc. Just random. Drove me bonkers

Incorrect teaching is not impossible