192 replies to this topic

[Iron_Scarecrow]

Yes that was the main problem. I really suspect there was a meaning in the original language it was written in that wasn't actually said but when translated into english it gets lost. Weird things like this always happen with translations I find.

[A. J. Raffles]

MdaG, on Nov 25 2005, 10:46 AM, said:

I'm still waiting for A.J. to comment on the Swedish phrasing 

Sorry, didn't realise that.
It's clearer, I think. "Andelen onyktra vid bad" seems less ambiguous to me than "the ratio of drunk people taking a bath". I may be wrong, though.

[MdaG]

A. J. Raffles, on Nov 25 2005, 01:06 PM, said:

MdaG, on Nov 25 2005, 10:46 AM, said:

I'm still waiting for A.J. to comment on the Swedish phrasing 

Sorry, didn't realise that.
It's clearer, I think. "Andelen onyktra vid bad" seems less ambiguous to me than "the ratio of drunk people taking a bath". I may be wrong, though.

*looks up ambiguous*
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.
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hmm maybe...

[A. J. Raffles]

It's the "vid bad" bit that does it, I think...

[Iron_Scarecrow]

We it not really important, we've sorted out the problem and can move on to more maths.

And to answer the original question when the thread was open: I have always liked maths, through years 7 to 10 I found math very easy as a subject, even topped my year in year 10 maths. But then year 11 and 12 the workload got too much for me to handle and I failed to learn anything at all.

[MdaG]

A. J. Raffles, on Nov 25 2005, 01:11 PM, said:

It's the "vid bad" bit that does it, I think...

I think the word "andel" might have a clearer meaning than "ratio". "vid bad" just means that the situation is about bathing.

To me ratio and andel have the same meaning. Proportion for example is better described by the word "Proportion". Ooooooh look!, it's the same word in Swedish as in English  

[A. J. Raffles]

MdaG, on Nov 25 2005, 11:17 AM, said:

A. J. Raffles, on Nov 25 2005, 01:11 PM, said:

It's the "vid bad" bit that does it, I think...

I think the word "andel" might have a clearer meaning than "ratio". "vid bad" just means that the situation is about bathing.

Yes, but I thought it made it clearer what "ratio" you meant.*shrug*

Well anyway, does anyone have a new problem?

[Iron_Scarecrow]

You could give this a go. But it very easy, basically just algebra. In the test I didn't bother with the first part as it was only 1 mark.

Oh I suppose you'd also have to know the conditions for volume to be a maximum.

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Edited by Iron_Scarecrow, 25 November 2005 - 11:51 AM.

[BeefontheBone]

I'll spoiler this one since I don't want to give it away:
Well, the first bit follows straight from the volume of a cylinder being its height (2h) times the area of the circular cross-section - they've even helpfully labelled the radius as x for you, and Pythagorus' Theorem gives us x^2 = R^2 - h^2, whence the area of the circle is pi(x^2), giving V as required.

The maxima of the volume function are given where dV/dh = 0, ie for 2pi{R^2 -3h^2}=0, which is solved by h= R/sqrt(3) (or - this, but since h is a length it cannot be negative).

Was that an AS paper?

[Iron_Scarecrow]

It was question 8 from the 2005 2 unit math test. Most important test in my school life (for maths that is), and unfortunately failed to study for it.

And yes you are right, although because it is 3 marks they would want to see every line of your working out but once you know the conditions for volume to be a maximum its then just basic algebra, I'm assuming Beef, that you can do algebra.

[BeefontheBone]

Well, it's simple calculus really - they don't teach it at GCSE level over here any more IIRC (my dad did it for his O-levels back in the day) which is fairly sensible since you don't need it until you go beyond school leaving age.
Yeah, I can pretty much do algebra

[Iron_Scarecrow]

And that's the 2005 HSC (Higher School Certificate) 2 unit math test actually.

I left out the important part, go me. Well about 70% of the year 12 2 unit math course has something to do with calculus. And I'm not the biggest fan of the amount of work solving a calculus problem requires.

[BeefontheBone]

Differentiation like that becomes second nature pretty quickly, to be honest. If you ever get the chance to do any complex analysis (well, if you don't like calculus I'd advise not taking it!) you'll see some complicated calculus - there's a really neat technique where you turn a horrible real integral which is near-impossible to solve by normal methods, turn it into a complex integral and do a bit of subtraction to get the answer dead easily. That really impressed me when I saw it in my second year at uni.

Is HSC what you'd do at 16 before leaving school? That bit of basic calculus wasn't on our equivalent syllabus when I did it, though I did teach myself some for a bit of coursework - was the easiest way to get full marks and do less work In fact, that was a question about maximising volumes I think.

[Iron_Scarecrow]

You do SC (School Certificate) at about 16. But that is to reach years 11 and 12, you can leave school to get a job then too. But HSC is what you do around 18 years of age and is the last year of school, you can choose to do it over 2 years or even 6 years, but most people just do it in the one year.

[MdaG]

BeefontheBone, on Nov 25 2005, 02:47 PM, said:

Differentiation like that becomes second nature pretty quickly, to be honest. If you ever get the chance to do any complex analysis (well, if you don't like calculus I'd advise not taking it!) you'll see some complicated calculus - there's a really neat technique where you turn a horrible real integral which is near-impossible to solve by normal methods, turn it into a complex integral and do a bit of subtraction to get the answer dead easily. That really impressed me when I saw it in my second year at uni.

Are you talking about making use of Cauchy's residue theorem?