View Full Version : What's the answer?

Mrs T

16th November 2015, 10:10 PM

I saw this on Simon Mayo's Facebook page and we had an interesting debate. I solved it one way and Mr T another. I don't know the answer but it certainly generated lots of comments!

6/2(2+1) = ?

Anyone know the right answer?

Amanda

Graham_of_Rainham

16th November 2015, 10:13 PM

BODMAS

*chr

Zuiko

16th November 2015, 10:37 PM

I saw this on Simon Mayo's Facebook page and we had an interesting debate. I solved it one way and Mr T another. I don't know the answer but it certainly generated lots of comments!

6/2(2+1) = ?

Anyone know the right answer?

Amanda

I don't know but my guess is that 6/2 can be simplified as 3 which is multiplied by the sum in the brackets (which is also 3). Therefore the answer is 9, or am I barking totally up the wrong tree? :o

Barr1e

16th November 2015, 10:57 PM

I don't know but my guess is that 6/2 can be simplified as 3 which is multiplied by the sum in the brackets (which is also 3). Therefore the answer is 9, or am I barking totally up the wrong tree? :o

Agreed. :)

Regards. Barr1e

Wee man

16th November 2015, 11:20 PM

I would go with that.

Mrs T

17th November 2015, 05:55 AM

I got 9 and Mr T got one but his maths is better on that sort of thing so I assumed he was right until I saw this this morning.

Looks like you guys were right too!

https://m.youtube.com/watch?feature=youtu.be&v=JPe1aBW_YCg

Amanda

Ross the fiddler

17th November 2015, 06:39 AM

I got 9 and Mr T got one but his maths is better on that sort of thing so I assumed he was right until I saw this this morning.

Looks like you guys were right too!

https://m.youtube.com/watch?feature=youtu.be&v=JPe1aBW_YCg

Amanda

It's rough when the 'man' has to admit he was wrong, (something I would never be :rolleyes: ;) ) but I would also agree with John as his solution is the convention when brackets are used.

It could also be solved as such

6 X (2 + 1)/2

= (6 X 3)/2

=18/2

=9

*chr

Phill D

17th November 2015, 06:48 AM

I remember BODMAS good to see some things don't change :)

pdk42

17th November 2015, 07:50 AM

I'm amazed anyone sees this as a "problem". It's GCSE yr 1 maths isn't it?

byegad

17th November 2015, 08:27 AM

6/2(2+1)

Could also be 1.

Read as 6 over 2(2+1) You'd get

=6 over 2x3

=6/6

=1

Zuiko

17th November 2015, 08:27 AM

I'm amazed anyone sees this as a "problem". It's GCSE yr 1 maths isn't it?

That's why I was hesitant with my answer; it's been a looooooong while since I was at school and I was wary that it might be some sort of trick question.

But when would you use an equation like that (let alone anything more complicated) in normal, everyday life? It's a good example of why I believe GCSE Maths should be split into two subjects; Basic Arithmetic for all pupils and more advanced Mathematics for those who plan a career where it is required.

Zuiko

17th November 2015, 08:29 AM

6/2(2+1)

Could also be 1.

Read as 6 over 2(2+1) You'd get

=6 over 2x3

=6/6

=1

Ah, I see. Yes, the way it is presented is ambiguous. :)

Wee man

17th November 2015, 08:51 AM

Can see both how you treat the / is the main focus, I would maybe go with 1 now!

Bikie John

17th November 2015, 08:56 AM

I would say that the problem is badly posed. Unless you are a whizz with the priority of operations (BODMAS as Graham points out) you could parse it with the (2+1) on the top or the bottom - and end up with 9 or 1. And even if you are just such a whizz yourself, it is unreasonable to assume that your readers will be. The implicit multiplication doesn't help make it any clearer.

If you actually care about the answer you add extra brackets and multiplication signs to make it unambiguous - 6/(2*(2+1)) or (6/2)*(2+1).

John (Who spent years trying to get trainee programmers to write their sums out in small steps, partly to avoid just this sort of confusion)

al_kaholik

17th November 2015, 09:09 AM

The son of one of the chaps in the office has just been doing his 11+ - this sort of thing came up. Interestingly, a handful of 40-55 year olds couldn't get the correct answer but all those of an age younger got there.

Otto

17th November 2015, 09:42 AM

The notation is badly drafted and as such the question is ambiguous. Solving the bracketed terms first gives 3, but the answer could be 6/2 x3 (nine) or 6/ 2x3 (one). Conventionally I suppose you work left to right so the correct answer should be 9 - which is what my calculator says it should be :). I would not base rocket science on such a question :D.

Funnily enough when I did my 11+ there was a question involving brackets and a division line. I had never seen such notation before so assumed the bracketed figures should be summed and the division line meant the lower sum should be subtracted from the upper. When I subsequently asked my parents about this, I was amazed to find the answer was the same whether it was obtained correctly or by my incorrect method!

Ross the fiddler

17th November 2015, 10:24 AM

6/2(2+1)

Could also be 1.

Read as 6 over 2(2+1) You'd get

=6 over 2x3

=6/6

=1

Only if it was written

___6___ =1

2(2+1)

Obviously it would depend how it was written but with 6/2(2+1) it may be a little ambiguous in its intent but essentially should be taken as 6/2 X (2+1) when written like that instead of 6/(2(2+1)).

That's my story & I'm sticking to it! :p :D

I could always start an argument about spelling too, like "Were you where you were supposed to be where you were told to be? I suspect there are some that might confuse the 'where & were' with the pronunciation of each as I think my old man seem to having come from above (north of) Wales. ;)

*chr

byegad

17th November 2015, 10:36 AM

My point exactly Ross. As to spelling???? Totally lost me on that one.

Jim Ford

17th November 2015, 10:37 AM

It's 6.

For the answer to be 1 it would need to be 6/(2(2+1))

Jim

Ross the fiddler

17th November 2015, 11:14 AM

My point exactly Ross. As to spelling???? Totally lost me on that one.

Maybe the NE is different from the NW. ;) It's more on the pronunciation that I think a Liverpuddlian might have been heard to say it differently (or used the wrong word) to the following.

where rhymes with stare, bear, care, fair, mare.

were rhymes with her, fur, stir, purr, burr, sir.

OK, I'll leave it alone. ;) :D

Ross the fiddler

17th November 2015, 11:18 AM

It's 6.

For the answer to be 1 it would need to be 6/(2(2+1))

Jim

You'd take a half a dozen every time, would you? ;) :D

OM USer

17th November 2015, 04:39 PM

6/2(2+1) = ?

Anyone know the right answer?

The question is posed in a very sloppy and ambiguous form. If it had been written as:

6 ÷ 2 * (2+1)

Then I think all of us would have got it correct. Even

6/2*(2+1)

would be better than the original as would the completely unambiguous

(6/2)(2+1)

The problem is in the interpretation of the missing multiplication operator (I have used the asterisk to denote the multiplication operator rather than "x" or ".") and whether its ommission implies some precedence. Intuition says that it might. Consider these two equations:

6 ÷ 2 * x

6 ÷ 2x

The rules of BODMAS clearly state that if x = (2+1) then the first equation has the value 9. However mathematicians would have the correct value of the second equation as 1 as "2x" is shorthand for "(2 * x)". Note the addition of the brackets which are needed when we re-introduce the multiplication operator as "2x" on its own implies precedence of the implicit multiplication.

We are left with the question, is:

2(2+1)

shorthand for

(2 * (2+1))

in which case

6÷2(2+1) = 6÷(2*(2+1)) = 6÷(2*3) = 6÷6 = 1