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PostPosted: Mon Oct 05, 2015 7:09 pm 
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Ben is 3 years older than his sister and a third of the age of his mother. His father is 4 years older than his mother and four times age of his sister. How old is Ben?


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PostPosted: Mon Oct 05, 2015 8:06 pm 
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Why don't you want to use algebra?


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PostPosted: Mon Oct 05, 2015 8:11 pm 
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mumsdarling2 wrote:
Why don't you want to use algebra?

I have solved the question by using algebra, but when I try to explain this to my 10 year old DS, he seems very confused. So I want to see if there is another way.


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PostPosted: Mon Oct 05, 2015 9:50 pm 
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I don't know.


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PostPosted: Mon Oct 05, 2015 11:10 pm 
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I drew a line with a mark a little bit in from the left labelled 'Sis'. Another mark a bit further over to the right labelled 'Ben'. At the right hand dot of the line, a mark labelled 'Dad' and little further to the left of 'Dad' a mark labelled 'Mum'.

As an aide memoire I put '?' under the section of line to the left of 'Sis', '3' between 'Sis' and 'Ben' and '4' between 'Mum' and 'Dad'. I then did 'hops' along the line to indicate that 'Ben' sits a third of the way from the left hand end to 'Mum' and 'Sis' a quarter of the way from that end to 'Dad'.

Having drawn the pretty picture to help visualise the problem, I just played around with ages for Ben, which when multiplied by 3 give an age for Mum four years less than the age for Dad (3 years less than Ben, ×4). It turns out that the siblings are just about the same ages as DD and DS2 and Mum and Dad are 8 and 5 years younger than myself and DH respectively :)

Possibly rather too long-winded for exam conditions, but it may help in transferring the solving of the problem to algebra, if that's what you want him to use.

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PostPosted: Tue Oct 06, 2015 5:53 am 
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For these type of questions I had to teach algebra to my son. There are many questions you will come across which needs to be done by algebra to be time efficient. My son says that he encountered many questions in exam that needed algebra knowledge.
Basic algebra would be enough.


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PostPosted: Tue Oct 06, 2015 11:32 am 
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ToadMum wrote:
I drew a line with a mark a little bit in from the left labelled 'Sis'. Another mark a bit further over to the right labelled 'Ben'. At the right hand dot of the line, a mark labelled 'Dad' and little further to the left of 'Dad' a mark labelled 'Mum'.

As an aide memoire I put '?' under the section of line to the left of 'Sis', '3' between 'Sis' and 'Ben' and '4' between 'Mum' and 'Dad'. I then did 'hops' along the line to indicate that 'Ben' sits a third of the way from the left hand end to 'Mum' and 'Sis' a quarter of the way from that end to 'Dad'.

Having drawn the pretty picture to help visualise the problem, I just played around with ages for Ben, which when multiplied by 3 give an age for Mum four years less than the age for Dad (3 years less than Ben, ×4). It turns out that the siblings are just about the same ages as DD and DS2 and Mum and Dad are 8 and 5 years younger than myself and DH respectively :)

Possibly rather too long-winded for exam conditions, but it may help in transferring the solving of the problem to algebra, if that's what you want him to use.


Yes, I too was thinking of a trial and error method along those lines too. Worth being able to do things that way too - particularly the drawing to help visualise the problem - but, as you say, a bit of a mess in a timed test.

Equations with words rather than letters could do the job too - but really that's algebra too and just harder to write out.


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PostPosted: Tue Oct 06, 2015 12:21 pm 
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I also have the thought that this is a test of the candidate's ability to apply what they should have off pat by this age (3- and 4-times tables, albeit extending then beyond 12x) with an ability to apply logical thought to the problem. Is algebra in the KS2 curriculum (old or new)? The 'if 2 apples and 3 pears cost 98p and 5 kumquats and a raspberry cost 64p, then...' type question doesn't really count.

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PostPosted: Thu Jul 14, 2016 6:46 pm 
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I have just come across this as well. Can someone please explain the algebra to me as we havent done that yet and could do with some help?

Thanks


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PostPosted: Thu Jul 14, 2016 8:05 pm 
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Googley2 wrote:
I have just come across this as well. Can someone please explain the algebra to me as we havent done that yet and could do with some help?

Thanks


This question has come up again in the last week or so. It's not really algebra.

http://www.elevenplusexams.co.uk/forum/11plus/viewtopic.php?f=15&t=47454&start=0

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