Login

Welcome, Guest. Please login or register.

March 29, 2024, 07:04:01 am

Author Topic: Maths Extension 1 solutions  (Read 9731 times)

0 Members and 1 Guest are viewing this topic.

keltingmeith

  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 5493
  • he/him - they is also fine
Re: Maths Extension 1 solutions
« Reply #15 on: October 31, 2020, 01:15:55 am »
I can do it on my calculator (fx100au) not sure if everyone else can. But do you reckon I'll lose any marks for having a more accurate answer compared to the "approximate" answer they wanted?

I mean, the difference between the two is 1%. It's tiny, minor, basically nothing - you can probably feel pretty safe in that you'll get it accepted.

On this, I'm not a HSC expert, but they should be aware that some of the calculators they allow can calculate z-scores like this, and so should be prepared to get answers like you have given.

RuiAce

  • ATAR Notes Lecturer
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 8814
  • "All models are wrong, but some are useful."
Re: Maths Extension 1 solutions
« Reply #16 on: October 31, 2020, 01:54:15 am »
I can do it on my calculator (fx100au) not sure if everyone else can. But do you reckon I'll lose any marks for having a more accurate answer compared to the "approximate" answer they wanted?
That was something I was genuinely not aware of. I had to look up the user guide to learn how to do standard normal probabilities on the fx-100AU plus. It looks like the standard normal is the only one it can do.

It also appears that the more classical fx-82AU plus II doesn't have this functionality. Which was probably why I never considered it for the fx-10AU plus - oops.

In theory, I would hope that it doesn't matter. The only thing I'd be worried about in practice is if NESA took that into consideration themselves as well (when writing down their list of approved calculators). If they knew that some calculators had this functionality, then they should know to mark accordingly to it wherever needed. Yet if they weren't aware, I would really hope they don't deduct marks for "pulling a number out of thin air" when it was just handy calculator knowledge.

That being said, I would hope that they know to actually compute \( P(-1.02\leq Z\leq 1.02)\) on statistical computing software, to check your answers against it. I'd lean towards it should be no problem; just not confident enough to guarantee anything sadly.

I mean, the difference between the two is 1%. It's tiny, minor, basically nothing - you can probably feel pretty safe in that you'll get it accepted.

On this, I'm not a HSC expert, but they should be aware that some of the calculators they allow can calculate z-scores like this, and so should be prepared to get answers like you have given.
But like, do you really call the entire expression \(P(Z\leq z)\) a '\(z\)-score', instead of just the \(z\) bit itself?
« Last Edit: October 31, 2020, 01:58:03 am by RuiAce »

keltingmeith

  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 5493
  • he/him - they is also fine
Re: Maths Extension 1 solutions
« Reply #17 on: October 31, 2020, 02:50:06 am »
But like, do you really call the entire expression \(P(Z\leq z)\) a '\(z\)-score', instead of just the \(z\) bit itself?

okay, no, you're right - the z-score is the little z, not the probability. Damn nerds and their semantics ::) (he says like he isn't doing a PhD)

hayleyason

  • Fresh Poster
  • *
  • Posts: 2
Re: Maths Extension 1 solutions
« Reply #18 on: October 31, 2020, 08:48:48 am »
Hi rui do you think a raw mark of 80 will be enough to get an E4?

cullen.l7

  • Fresh Poster
  • *
  • Posts: 1
Re: Maths Extension 1 solutions
« Reply #19 on: October 31, 2020, 09:03:18 am »
Hey Rui! In question 11(a)(ii) I think you had a bit of a transcription error between lines, I believe the final answer should be (x-2)(x^2+5x+3) not (x-2)(x^2-5x+3)

erick rajan

  • Fresh Poster
  • *
  • Posts: 1
Re: Maths Extension 1 solutions
« Reply #20 on: October 31, 2020, 09:22:36 am »
For question 11C, where you are required to graph the reciprocal of the parabola, from memory the parabola is drawn with a restricted domain and range (there are no arrows indicating it extends to infinity).

So I'm pretty sure the reciprocal function likewise shouldn't extend to infinity.

Also can someone drop the link to the paper...

sweetiepi

  • National Moderator
  • ATAR Notes Legend
  • *****
  • Posts: 4767
  • "A Bit of Chaos" (she/they)
Re: Maths Extension 1 solutions
« Reply #21 on: October 31, 2020, 10:14:49 am »
Also can someone drop the link to the paper...
Unfortunately, you're going to have to wait for NESA on that one, as we can't distribute NESA papers on the forum. :)
2017-2019: Bachelor of Pharmaceutical Science (Formulation Science)
2020: Bachelor of Pharmaceutical Science (Honours) Read my uni journey here!

RuiAce

  • ATAR Notes Lecturer
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 8814
  • "All models are wrong, but some are useful."
Re: Maths Extension 1 solutions
« Reply #22 on: October 31, 2020, 12:21:39 pm »
okay, no, you're right - the z-score is the little z, not the probability. Damn nerds and their semantics ::) (he says like he isn't doing a PhD)
What even is a PhD :o
Hi rui do you think a raw mark of 80 will be enough to get an E4?
It's possible at least. 80 raw has been enough in the past. Fingers crossed that it does though. I was actually originally thinking 81 or 82, but I won't rule out 80.

I have a feeling it comes down to how many people screwed up the combinatorics. That seems to be what would push down the average mark the most. (Of course don't go wishing misfortune on your peers or anything! It's just a suspicion.)
Hey Rui! In question 11(a)(ii) I think you had a bit of a transcription error between lines, I believe the final answer should be (x-2)(x^2+5x+3) not (x-2)(x^2-5x+3)
Whoops, my bad! Will be fixed in a min.
For question 11C, where you are required to graph the reciprocal of the parabola, from memory the parabola is drawn with a restricted domain and range (there are no arrows indicating it extends to infinity).

So I'm pretty sure the reciprocal function likewise shouldn't extend to infinity.

Also can someone drop the link to the paper...
You're right in that there weren't arrows. I think more accurately my answer should've just ignored the arrows. NESA seems to also ignore arrows in these scenarios (from looking at a few past papers).

I've never interpreted that as a restricted domain though. To me, restricted domain always meant you had to plot the coordinates of the endpoints. Which they did not do. I interpret what they did as the ambiguous case where I really should not make any assumptions on if the graph stops, or extends to infinity. I would hope that they accept both answers in this scenario.

mrsc

  • Adventurer
  • *
  • Posts: 15
Re: Maths Extension 1 solutions
« Reply #23 on: October 31, 2020, 01:06:34 pm »
What do you guys reckon the cutoff for e4 will be this year considering many people were stumped by question 14 (a) (including myself)

BakerDad12

  • Trendsetter
  • **
  • Posts: 126
Re: Maths Extension 1 solutions
« Reply #24 on: October 31, 2020, 02:09:06 pm »
RuiAce said he thinks it would be 80-82. In the raw marks database, a raw 74 aligned to 90 in 2019. Was their exam significantly harder than the rest?

hayleyason

  • Fresh Poster
  • *
  • Posts: 2
Re: Maths Extension 1 solutions
« Reply #25 on: October 31, 2020, 02:22:35 pm »
RuiAce said he thinks it would be 80-82. In the raw marks database, a raw 74 aligned to 90 in 2019. Was their exam significantly harder than the rest?
yeah I saw that as well

RuiAce

  • ATAR Notes Lecturer
  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 8814
  • "All models are wrong, but some are useful."
Re: Maths Extension 1 solutions
« Reply #26 on: October 31, 2020, 02:31:10 pm »
I just had a look. I do think 2019 was a bit harder actually; it felt like more questions stood out (multiple choice as well). In this year’s paper, it was really just the combinatorics.

Although, 74 aligning to 90 is a bit unexpected; I don’t think it was that hard. Perhaps I did overestimate the cutoffs then. But we shall see.