Talk

Calling math teachers! 4+6÷2=?

(10 Posts)
cricketballs Mon 09-Nov-15 16:34:42

There is a current thread in chat [http://www.mumsnet.com/Talk/_chat/2504038-4-6-2 here]] asking this question. I was always taught it work left to right and therefore my answer is 5 - what is this BIDMAS that everyone is arguing about?! What is the real answer?

CrotchetQuaverMinim Mon 09-Nov-15 16:44:29

People there are not arguing about the answer, really. The question there is more about whether you can say the question in different ways in order to imply that it should be done in a certain order (i.e., implying brackets), which I think you easily can.

As a written problem, if there are no brackets, you should do multiplication or division first, before you do addition/subtraction. If there are brackets, you should do those first. If there are powers, roots, etc, then you do those after the brackets. The BODMAS and similar acronyms are just ways to remember that - it's nothing new. Many people were taught how to do the problems correctly, but without the acronym, or just by calling it 'order of operations'.

CrotchetQuaverMinim Mon 09-Nov-15 16:45:34

(i.e., as a straightforward written problem, with no other indications, then the answer is 7. With brackets, or tone of voice implying such, or context implying them, etc., then the answer would be 5).

SuffolkNWhat Mon 09-Nov-15 16:46:16

I'm teaching BIDMAS at the moment and the answer is 7 as it is written down.

cricketballs Mon 09-Nov-15 16:49:40

So I was taught incorrectly then good job I don't venture near the math's rooms

insameboattoo Mon 09-Nov-15 16:53:50

Bodmas so multiply/divide first before adding so 7

GreenSand Mon 09-Nov-15 17:03:51

That thread is basically saying if you write a mathematical sentance badly, many people get the wrong answer. In a strictly mathematical sense, you do brackets, orders/indices, division, multiplication, addition then subtraction (BODMAS). However many people read it as a sentance, and get it wrong.

It actually means 4+(6/2), but many people read it as (4+6)/2.

CrotchetQuaverMinim Mon 09-Nov-15 17:45:23

I think it's perfectly plausible to imply brackets by using tone within a spoken sentence, though, and in real life, that's almost certainly what people do. It can mean (4+6)/2, if you give it the right intonation. The BODMAS rule is there for written problems where there would otherwise be ambiguity (so you need to add the brackets if you want the 4 and 6 added first).

The question there was about spoken sentences, and the phonetics involved - and how you can change the meaning by adding different emphasis, tone, etc.

MrsUltra Mon 09-Nov-15 19:37:52

The answer is obviously 7, but it is contrived way to do it and only for the purpose of testing - in the real world you would reorder it or put brackets - only in a artificial situation would you want to trick people into getting it wrong.

Mon 16-Nov-15 16:21:23

cricketballs

Try this on your computer's calculator - do it with the calculator on 'standard', then change it to scientific, you will get both answers.

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