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 Post subject: How to answer this question?Posted: Wed Nov 09, 2005 2:37 pm
My son is practicing for 11+ in 2 grammar schools. In one of the sample maths practice papre I have seen questions like the following:

11 + 5 - 7 x 8 - (14 ÷ 7) = ?

I know the expression within the brackets should be done first. What is the sequence after that? Is it starting from the left and work towrds the right OR do the multiplication and division followed by the addition and subtraction?

According to his maths teacher it is left to right, after working out the brackets first. But my experience with the computers reminds me otherwise. So I would like to get it clarified as to what is the correct way of doing it for the 11+ maths exam.

Regards,
SB

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 Post subject: InterestingPosted: Wed Nov 09, 2005 3:03 pm
Can I ask from which practice paper the question is from, with the question number and page number? (NFER, BOND)

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 Post subject: Maybe this is it .... maybe not?!Posted: Wed Nov 09, 2005 3:33 pm
The Rule to apply/remember is BODMAS/BIDMAS in terms of how to complete such a question:

DO FIRST to LAST ORDER
B = Brackets
O/I = Of or Indices (none in the question you are asking)
D = Division
M = Multiplication
S = Subtraction

Hence your question will go like this:

11 + 5 - 7 x 8 - (14 ÷ 7) = ?

do BRACKETS, DIVISION

=> 11 + 5 - 7 x 8 - 2 =

do MULTIPLY

=> 11 + 5 - 56 - 2 =

=> 16 - 56 - 2 =

do SUBTRACTIONS

=> -42 !

This is an unlikely outcome since its a minus number, and 10 year olds unlikely to be have been taught this end of the numbering system.

What was the text book answer?

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 Post subject: Posted: Wed Nov 09, 2005 3:49 pm
Hi Guest (Maths Hats On)

Thanks for the reply. Your answer is what I was thinking originally before his teacher twisted it the other way around.

The question I posted wasn't exactly from a question paper. I just made it up. But the following questions are from 'Kings school Chester' Maths entrance exam conducted on Saturday 7, February 2004. This question was downloaded from the school website following a link posted on this site: http://www.kingschester.co.uk/admission ... nation.htm

7 x 9 - 56 (11÷ 3) = ?

24 - 13 + 7 X 3
------------------ = ?
4 X (7 - 5)

One of the schools where my son is taking the 11+ exams is Sutton Grammar school and there is a maths paper of their own format. At present I do not have much idea about the content of the test.

Regards,
SB

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 Post subject: Posted: Wed Nov 09, 2005 4:53 pm
I have looked at these before, and you should work from left to right, but do the brackets first. At year 6 level children will not have been taught BIDMAS. I taught my child BIDMAS and she kept getting the wrong answer and it was because she wasn't working from left to right. They will then learn BIDMAS at secondary school.

BIDMAS - Bracket Index Divide Multiply Addition Subtraction.

As a secondary maths teacher I found it really hard to ignore BIDMAS, but I had to!

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 Post subject: Posted: Wed Nov 09, 2005 5:24 pm
Hi Guest,

That's a good point. I tried to explain it to my son and he wasn't going anywhere.

From your experience, if there was a question of this type in the 11+ exam, which method would the secondary schools apply to get the correct answer - BIDMAS or Left to Right? That is what matters in this case. I hope there won't be a question of this type. The common questions I have seen so far have the multiplication/division at the start of the expression and not in the middle or towards the right.

Regards,
SB

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 Post subject: Posted: Wed Nov 09, 2005 5:44 pm
This is really interesting. My son was taught to work from left to right at primary school. He's just started Year 7 and is now being taught BODMAS (or whatever it is!). In his first assessment he went back to old habits and did the left to right method and got all the questions in that section wrong (!). I'm just wondering why they're taught one thing in primary and another in secondary...???

To answer your question, he would have done the left to right method in his 11+ tests.

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 Post subject: BODMAS/BIDMASPosted: Wed Nov 09, 2005 7:33 pm
I've come across these sort of issues before in many sample papers.

A good question compiler for a formal 11+ exam should, strictly speaking, write an question in an unambiguous way using an appropriate number of brackets. Otherwise this would be picked up by the exam moderators and markers. (Assuming 11+ exams are moderated!)

It certainly would be for formal GCSE or A Level exams if there were alternative satisfactory answers.

If the question is ambiguous then there is only one mathematically correct answer - BIDMAS must be applied and that answer is correct. Just because a topic hasn't been taught as part of the Key Stage 2 National Curriculum is no excuse for giving a mathematically incorrect answer!

KenR

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 Post subject: Posted: Thu Nov 10, 2005 9:05 am
Hi KenR and Guest,

Very valid points in your replies. Last night I went through all such arithmetic equations I can find in the practice papers (other than school specific test papers) and found all are clear and unambiguous. So I hope it stays that way for the exams.

Regards,
SB

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