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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE General & Further Mathematics => Topic started by: kenhung123 on October 31, 2010, 03:49:01 pm

Title: Matrix Issue
Post by: kenhung123 on October 31, 2010, 03:49:01 pm
OK this neap matrix question has stumped me.

Could someone who understands explain this to me?

Answers are D B respectivelyq
Title: Re: Matrix Issue
Post by: _avO on October 31, 2010, 03:52:02 pm
I think the first one is A, not sure about the 2nd one First one is D

I think the second one is D?
Title: Re: Matrix Issue
Post by: lorcan_raven on October 31, 2010, 04:30:47 pm
For the first one, the 4x5 matrix would score the amount of times that each unit of scoring occurs - and then this NEW matrix would be how many POINTS for those type of units for each team to get a total.

Now, with the original matrix being 4x5, you can only PRE-multiply this transition matrix if it has (1x4) so that the multiplication of the two matrix is defined.
Conversely, if you are POST-multiplying it would need to be (5x1) for the opposite reason - however there are only 4 values for the scores so this is not going to work.

Matrix A has 5 values so it's wrong.
Matrix B is 4x1, when it needs to be 1x4 for pre-multiplying.
Matrix C is 1x4, when it needs to be 5xsomething which wouldn't work anyway.
Matrix E is just wrong from the get go - you can't add a matrix to transition into totals.

Therefore it's Matrix D, which has the correct 1x4 for pre-multiplying.

As for the second question, I am legitimately thrown by that one :S
Does it have any working out for that answer?
Title: Re: Matrix Issue
Post by: TyErd on October 31, 2010, 04:46:45 pm
for the first one, D sounds right, second question is a wtf question. So fkn confusing
Title: Re: Matrix Issue
Post by: crayolé on October 31, 2010, 04:57:09 pm
Yeah D for the first one, I got D for the second one too  EDIT: B maybe?

ABC -the percentage difference would be different for each year as the proportion of market share for each company would constantly change

Even if they were relative. By looking at the respective rows and columns, X loses .2 market share to other companies but gains .3 from them. Y loses .25 but gains .25 as well. Z loses .2 and gains .1/

D or B are the only ones I can see that would fit the criteria. Although I dont like that definitive nature of 'all' in that answer as it wouldnt be the case if Y had 100% market share from the start
Title: Re: Matrix Issue
Post by: shokstar on October 31, 2010, 05:03:31 pm
It cant be D, because you dont know what they start with...? It says at all times, which includes the initial state..

...doesnt it?
Title: Re: Matrix Issue
Post by: shokstar on October 31, 2010, 05:07:55 pm
I think by B, they mean that 10% of Z go to Y every year, just they worded it really badly,
Title: Re: Matrix Issue
Post by: Blakhitman on October 31, 2010, 05:09:18 pm
I think by B, they mean that 10% of Z go to Y every year, just they worded it really badly,

Yep, that's how I understood it too.
Title: Re: Matrix Issue
Post by: crayolé on October 31, 2010, 05:11:26 pm
I think by B, they mean that 10% of Z go to Y every year, just they worded it really badly,
Yeah I got that too but theres so much ambiguity in that answer.
I suppose B is the only one that works all the time. If you interpret it the correct way
Title: Re: Matrix Issue
Post by: kenhung123 on October 31, 2010, 05:16:49 pm
Yeah D for the first one, I got D for the second one too  EDIT: B maybe?

ABC -the percentage difference would be different for each year as the proportion of market share for each company would constantly change

Even if they were relative. By looking at the respective rows and columns, X loses .2 market share to other companies but gains .3 from them. Y loses .25 but gains .25 as well. Z loses .2 and gains .1/

D or B are the only ones I can see that would fit the criteria. Although I dont like that definitive nature of 'all' in that answer as it wouldnt be the case if Y had 100% market share from the start
Answer is B for some reason
Title: Re: Matrix Issue
Post by: kenhung123 on October 31, 2010, 05:19:12 pm
I think by B, they mean that 10% of Z go to Y every year, just they worded it really badly,
Oh right! OK thanks guys for the help!