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HSC 2015 MX1 Marathon (archive) (1 Viewer)

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Drsoccerball

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Re: HSC 2015 3U Marathon

Not sure what to do to get the marks:

 

InteGrand

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Re: HSC 2015 3U Marathon

Surely my school didnt expect the cohort to know this?...
The HSC is not meant to be allowed to ask you to explicitly solve the differential equation. It's meant to only be allowed to get students to verify that a given equation satisfies the differential equation.

If you have a copy of the 3U Year 12 Cambridge (Pender) maths textbook, check Exercise 7H page 281, the Extension exercise Q.11 there guides you through the method to solve that differential equation.
 
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Drsoccerball

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Re: HSC 2015 3U Marathon

The HSC is meant to not be allowed to ask you to explicitly solve the differential equation. It's meant to only be allowed to get students to verify that a given equation satisfies the differential equation.
so this is considered in the sylabus
 

InteGrand

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Re: HSC 2015 3U Marathon

so this is considered in the sylabus
No, as far as I know they're meant to only be able to give you the solution function, and then ask you to show that it satisfies the given differential equation by differentiating it etc.

The HSC isn't meant to be able to just get you to solve that differential equation from scratch, as far as I know.
 
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InteGrand

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Re: HSC 2015 3U Marathon

But this question was in my schools exam :/?>
Yeah, it may be possible that schools can do whatever they like (I'm not sure though)...lol.

Maybe your teachers had set Exercise 7H of the Year 12 3U Pender textbook as homework and told you to look at Extension or something?
 

Drsoccerball

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Re: HSC 2015 3U Marathon

Yeah, it may be possible that schools can do whatever they like (I'm not sure though)...lol.

Maybe your teachers had set Exercise 7H of the Year 12 3U Pender textbook as homework and told you to look at Extension or something?
we use fitzpatrick
 

InteGrand

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Re: HSC 2015 3U Marathon

we use fitzpatrick
Well did anyone manage to get out that question? If not, it doesn't make much difference. Or you could show the syllabus to your teacher or whoever wrote the paper.
 

leehuan

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Re: HSC 2015 3U Marathon

Although separation of variable is technically not in the 3U syllabus (a definite integral method is sometimes taught in 4U), you don't need it anyway.



It just makes the working tidier than what I just did.

And it also helps that this is a first order diff. eqn.
 
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photastic

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Re: HSC 2015 3U Marathon

Although separation of variable is technically not in the 3U syllabus (a definite integral method is sometimes taught in 4U), you don't need it anyway.



It just makes the working tidier than what I just did.

And it also helps that this is a first order diff. eqn.
We learnt this method for 3U. It wasn't hard, kinda more interesting but was a waste of time considering the HSC exams only use differentiation and actually provide the equation in a sense
 

Drsoccerball

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Re: HSC 2015 3U Marathon

Although separation of variable is technically not in the 3U syllabus (a definite integral method is sometimes taught in 4U), you don't need it anyway.



It just makes the working tidier than what I just did.

And it also helps that this is a first order diff. eqn.
Didn't see this when i was solving D:
 

leehuan

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Re: HSC 2015 3U Marathon

Please tell me where I went wrong:



 

InteGrand

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Re: HSC 2015 3U Marathon

Hey guys, could someone please explain to me the solution to Carrotsticks' 2014 trial question? http://puu.sh/ijqqn/efd1be7108.png

The solution is http://puu.sh/ijqnF/0c9662c363.png but there is no diagram.

I can't get my head around it - I've only used the divider method for doing simple things like assorting rings onto hands/into boxes etc.
Maybe I've misinterpreted the Q or screwed up some working out, but I'm not sure why the answer is .

Say we had k = 2 (so two different numbers from 0-9 used), and n = 3 (three-digit password).

Let's just say for now the two distinct digits used were 1 and 2. Since n = 3, these are the possibilities: 112, 121, 211, 221, 212, 122. That's 6 possibilities.

But we could do the same for all possible choices of two distinct digits. So it seems like the total possible ways for n = 3, k = 2 is: . But this doesn't agree with the answer, since .

Edit: My bad, Q said combinations, not permutations
 
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