Suggested Answers to the HSC 2016 Mathematics Exam (+Discussion!)

[treesap]

No, you're correct

[jamonwindeyer]

why did you change 15 a to 56pi/3? shouldn't it be 40pi/3? the y is already squared you dont have to sqaure the 9 again! it's 1/9 not 1/81. but please correct me if im wrong.

Hey! Woops, sorry about that, must have had a version cross when editing the formatting this morning; managed to upload one of my first versions of the solutions from prior to upload; just changed it back! Sorry for confusion

Question 15a is incorrect, for whatever reason you decided to square root the curves, and in doing so took out 1/9 but you didnt square root this. If you are going to do this method it should be 1/3 outside the sqrt(36-4x^2). Although I dont know why you have done this in the first place, we are asked for volume which requires y^2 anyway.

Technically, to perform a volume of revolution you should consider a function; which these aren't. To be most correct I first considered only the top half of \(C_1\) and \(C_2\), and then squared these in the formula. You are right, it gives the same result though! They wouldn't have enforced this in the HSC marking mind you, just going straight to \(y^2\) and \(x^2\) is definitely okay too

Good catch on the intermediate error though; I'll tidy that up for sure! But the answer is correct (as of the edit I've just made, again, sorry for the confusing version cross)

[becryan]

What would a 79 exam mark scale to?

[jamonwindeyer]

What would a 79 raw mark scale to?

Welcome to the forums!! Probably the mid 80's? Your best source for trends in previous years is here

[WLalex]

Hey Jamon, or whoever else

I was wonder if you could enlighten me on how our internal mark/rank from the school will influence your overall HSC mark that we get (the one the determines which band we get etc) e.g.  like if it will increase or decreased based on our rank from school or what not

[RuiAce]

Hey Jamon, or whoever else

I was wonder if you could enlighten me on how our internal mark/rank from the school will influence your overall HSC mark that we get (the one the determines which band we get etc) e.g.  like if it will increase or decreased based on our rank from school or what not

Your external marks influence your internals. Not vice versa.

Once moderation has happened and your internals are adjusted, after some alignment you get your overall HSC marks.

Scaling guide by Jamon

[bugsbuggy]

Hey everyone! i'm looking at 88 internal and 87-90 for the hsc. would that align to a band 6 by any chance? Thanks in advance!

[RuiAce]

Hey everyone! i'm looking at 88 internal and 87-90 for the hsc. would that align to a band 6 by any chance? Thanks in advance!

In saying that I completely disregarded your internal mark because moderation hasn't happened yet.

As for your externals, from the raw marks database it is clear that in general, 87 raw aligns to 90 or 91.

[CC2095]

Question 16B

You have 10<y<200
should be 10<=y<200

[CC2095]

Q11b

denominator should be 3x - 4 not 3x + 4

[jamonwindeyer]

Question 16B

You have 10<y<200
should be 10<=y<200

I'm leaving this one as it is, because the question says the function is valid after the yabbies are introduced. Speaking strictly this excludes \(t=0\). I'm probably reading too far into the question, but yeah, I'll leave it for now. Not a huge deal

Q11b
denominator should be 3x - 4 not 3x + 4

Touche! I'll fix this up today, good spot

Welcome to the forums!