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 Post subject: HABS maths exam 2009
PostPosted: Mon Oct 18, 2010 8:18 pm 
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Joined: Sat May 02, 2009 6:14 am
Posts: 44
Can anybody help me out with question 30 of the above paper please?
It relates to the various combinations possible of 4 people seated around a table.
DS and I managed to work out the first part and got stuck on the 2nd part.
Any help gratefully received!
Thanks.


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 Post subject: Re: HABS maths exam 2009
PostPosted: Mon Oct 18, 2010 9:31 pm 
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Joined: Fri Oct 30, 2009 11:08 pm
Posts: 1226
Maths rusty but I think:


Part 2 - In part 1 there were four options, but Archibald only had one choice of seat. This time he has four choices therefore there are 4 x 4 = 16 possibilities.

Part 3 - First seat 4 possible occupants, second seat 3 , third seat 2, last seat only one

so 4 x 3 x 2 x 1 = 24


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 Post subject: Re: HABS maths exam 2009
PostPosted: Mon Oct 18, 2010 9:47 pm 
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Joined: Thu Jan 03, 2008 8:26 am
Posts: 1326
Location: Watford, Herts
We can simplify by seating in the order BCDA. B has 4 choices of seat. For each of these, C has 2 choices, and for each of those D has two choices, leaving only 1 seat for A. Therefore there are 4x2x2x1 = 16 possibilities.


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 Post subject: Re: HABS maths exam 2009
PostPosted: Tue Oct 19, 2010 8:44 am 
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Joined: Mon Apr 28, 2008 9:57 am
Posts: 223
It would have been great if Habs provided answers to their papers, will certainly make life easier for a maths novice like me :P


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 Post subject: Re: HABS maths exam 2009
PostPosted: Tue Oct 19, 2010 8:18 pm 
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Joined: Sat May 02, 2009 6:14 am
Posts: 44
Thank you
How do I explain to DS why we need to multiply the possibilities?
I understand that in each place there will be different options but why do we need to multiply these?
This sort of question occurs in other papers also eg possible combinations from different coloured marbles
Does anybody have an easy way to explain to a 10 year old?


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 Post subject: Re: HABS maths exam 2009
PostPosted: Wed Oct 20, 2010 12:19 pm 
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Joined: Sun May 09, 2010 12:04 pm
Posts: 2615
Sorry, I am really a novice in this 11+ preparation. I have never heard about these HABS maths papers and I had a quick look in the shop but I haven't been able to spot them. :x
What are they exactly? Are they harder than Bonds maths exams? Are they specifically used in some counties or can anybody preparing for 11+ in England benefit from using them? :?:


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 Post subject: Re: HABS maths exam 2009
PostPosted: Wed Oct 20, 2010 12:23 pm 
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Joined: Tue Sep 01, 2009 3:38 pm
Posts: 2083
Location: Maidstone
http://www.habsboys.org.uk/info/examina ... 11plus.php :wink:

_________________
Impossible is Nothing.


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 Post subject: Re: HABS maths exam 2009
PostPosted: Thu Oct 21, 2010 12:37 pm 
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Joined: Sun May 09, 2010 12:04 pm
Posts: 2615
Oh I see!! Thanks, Sherry ! :D


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