Q3(a) WTF!!!! (1 Viewer)

[physician]

The root is between 0.725 and 0.75, so to one decimal place, it must be 0.7.

Agreed. I think i was confused because I got an answer that when rounded off to 1 dec place gave 0.7, so i thought it was wrong and I think I just stopped, I cant even remeber, neverthless, i'll only get one mark for the working out..I doubt i put the answer as 0.7, however, Yes! the answer is 0.7, using more than one application of halving the interval method shows this!

 

[Abtari]

yea what wanton-wonton did was right..

you half it then half it again (to check your answer)

and its def 0.7...
it was actually in an old hsc where they did the same thing and people got tricked with the same thing....

this is what this yrs's maths was all about - help put off people, so only the best shine.

pfft..
as opposed to other yr's maths exams which weren't about putting off people - which were about making sure that everyone shined. rite...

 

[EvilDude]

that question was horrifically worded. they should, in theory, accept both 0.7 or 0.8 as the right answer.

yes sure the question didn't say used the method ONCE. BUT, it also didn't mention anything about a BETTER or CLOSER approximation either!
so any approximation (within reason) should be acceptable, otherwise the question can be construed as misleading.

also, the word "approximation" means exactly that - an approximation. so since the question didn't mention a "better" or "closer" approximation, then that's no reason to discriminate one approximation over the other. as long as one showed the working for halving the interval, then x = 0.8 should be quite a reasonable approximation in theory.

The question is worded (IMO) saying yes the root is an apprxiumation however, it is as close as you can get to one decimal place. "Correct to 1 d.p" From the process twice, the root to one decimal is obviously 0.7. I don't mind if they accept 0.8 but they should accept 0.7 as it is the right answer.

 

[Abtari]

yeah i agree...they should accept 0.7, but they should accept 0.8 as well

 

[Slidey]

that question was horrifically worded. they should, in theory, accept both 0.7 or 0.8 as the right answer.

yes sure the question didn't say used the method ONCE. BUT, it also didn't mention anything about a BETTER or CLOSER approximation either!
so any approximation (within reason) should be acceptable, otherwise the question can be construed as misleading.

also, the word "approximation" means exactly that - an approximation. so since the question didn't mention a "better" or "closer" approximation, then that's no reason to discriminate one approximation over the other. as long as one showed the working for halving the interval, then x = 0.8 should be quite a reasonable approximation in theory.

Aha! I agree whole heartedly. I too sat there thinking about this for a while.

 

[who_loves_maths]

^ well i'm glad you'd agree Slide
it seems to me as if this question was just put there to "trick" ppl - which doesn't say a lot about the standard of the exam. the point shouldn't have been to fool ppl into doing the wrong thing.
i'm sure had it been worded more aptly, that most ppl would have done the 'right' thing. it's not like ppl don't know how to use the 'halving-the-interval' method.

so even if the ppl who put 0.8 down would eventually lose a mark, it still says nothing about our understanding of that part of the course - making that question stupid and meaningless. it didn't test knowledge at all

(i have a strong suspicion that examiners will not accept 0.8... *sigh* how cruel.)

 

[who_loves_maths]

Originally Posted by xrtzx
WLM, is gonna top mx1 and mx2 this year, i'll put my money on that

lol, IF ONLY!!!

nice one mate (and you shouldn't waste money like that. it's precious )

Originally Posted by aural_sax05
WLM, howd u find it?

and howd u find 4u?

im sure u did well bud

judging from my response above to xrtzx, i'm sure you can tell the following:

4u: catastrophe ! (no thanks to many things )
3u: disaster ! (no thanks to that approximation question )


in fact, to be honest, i'm anticipating a better result from English Advanced!!! ... how paradoxical ...

 

[rama_v]

I put 0.7
I did the halvign the interval method twice, and found that the root lies between 0.7 and 0.75. Hence it needed to be rounded down. It really came in handy that I read up on the 1996 examination report yesterday night though:

The question was suspiciously similar:
1996 HSC 2(a) Teh function f(x) = x³ - ln(x+1) has one root between x = 0.5 and 1
(i) Show that the rot lies between 0.8 and 0.9
(ii) Hence use the halving-the-interval method to find the value of the root,
correct to one decimal place.

Now, here are the comments:
"Candidates who scored 10 or 11 marks most frequently lost the mark(s)
here. Very many candidates failed to realise that any number between 0.85
and 0.9 rounds up to 0.9, and continued the process for many repetitions,
often concluding for example ‘root is 0.875 correct to 1 dec. pl.’ or ‘root is
between 0.85 and 0.9 \ 0.8 to 1 dec. pl.’"

In that instance the instruction was to round up. In this instance, i dare say that they are looking to round down.

 

[richz]

i'm sure you can tell the following:

4u: catastrophe ! (no thanks to many things )
3u: disaster ! (no thanks to that approximation question )


in fact, to be honest, i'm anticipating a better result from English Advanced!!! ... how paradoxical ...

"4u: catastrophe ! (no thanks to many things )" does this mean >110/120
"3u: disaster ! (no thanks to that approximation question )" does this mean 83/84

wlm, u and slide rule are the smartest people on this forum. if u dont top both u'll fo shizzle get a top 10 ranking for both

 

[icycloud]

Can't you just write "if one application is used, then the approximation would be 0.8 (1dp), but further applications of the method would result in an approximation of 0.7 (1dp)".

 

[kyu_chan]

>_< I studied Newton's method more... but I got it at the end I think

 

[UltimateWarrior]

I'm pretty sure I put 0.7 as the approx. to one decimal place. I got g(0.7) > 0 and g(0.75) < 0 so the root is between 0.75 and 0.7. So its 0.7 to one dec place?

 

[wanton-wonton]

Will we all stop arguing over this question, it really isn't that exciting.

 

[who_loves_maths]

Originally Posted by xrtzx
wlm, u and slide rule are the smartest people on this forum. if u dont top both u'll fo shizzle get a top 10 ranking for both.

haha... let's not stretch the truth that far shall we?

but in terms of Slide_Rule, yes i agree, he's probably the smartest on this forum in maths
of course, this means the 4u and 3u exams are not real testers of talent nor creativity in mathematics - rather, simply effort and discipline. (which i guess are also important.)

and let's face it xrtzx, you ain't bad yourself at maths either . srsli.

 

[richz]

ooo wlm, ur so modest

yes imo im not a very bad mathematician, but not a good one too. Im afraid my marks will not reflect that, for 4u i failed miserably :'(, but it doesnt help if u dont get enough sleep the nite before, lol dont know wat i was doing didnt even study on the weekend was watching the v8s, hmmm.. i regret that ..... 3u did alrite, but there are always silly mistakes to be found

 

[who_loves_maths]

Originally Posted by xrtzx
yes imo im not a very bad mathematician, but not a good one too. Im afraid my marks will not reflect that, for 4u i failed miserably :'(, but it doesnt help if u dont get enough sleep the nite before, lol dont know wat i was doing didnt even study on the weekend was watching the v8s, hmmm.. i regret that ..... 3u did alrite, but there are always silly mistakes to be found

^ hahaha... of course it doesn't reflect your true abilities - this is the HSC we're talking about lol.
and as with silly mistakes, well, we're all only human... i make a lot too

 

[richz]

off topic whats with everyone changing their hsc year to 2010, ff, estel and now u??

 

[who_loves_maths]

^ it's cause we want to forget HSC '05

hehe... but on second thought, you're right... i don't even know why i did that... hmm...

 

[香港!]

WoW! Nice fishy there!!

How did you go today who_loves_maths ??

 

[who_loves_maths]

^ hey 香港!, actually i like my other pic of the pig better

as with 3u, Re:

Originally Posted by who_loves_maths
4u: catastrophe ! (no thanks to many things )
3u: disaster ! (no thanks to that approximation question )