Math Ext 1 Predictions/Thoughts (2 Viewers)

notme123

Well-Known Member
Joined
Apr 14, 2020
Messages
1,002
Gender
Male
HSC
2021
Also, slightly controversial, I quite liked the sample proportion question as it really tested whether you knew your stuff conceptually. Most sample proportion questions are pretty generic just blindly plugging numbers into formulae.
do you think getting the answer of 6000 would be sufficient for 3 marks regardless if we had any errors with inequalities in our working??
 

CM_Tutor

Moderator
Moderator
Joined
Mar 11, 2004
Messages
2,644
Gender
Male
HSC
N/A
Looking at the solutions provided above:
  • there is a small error in Q5 where as , but the solution writer has stated that . This is because . Thus, the angle must be obtuse or - the solution writer is correct that NESA have made a mistake in including in the category of "obtuse" angles.
  • In q11(h), though it is not in the syllabus, a potentially simpler solution is:
  • Per the discussion above, q12(a) appears wrong​
  • the handling of the absolute value in q12(b) is wrong as the temperature is increasing towards 25, hence and the equation is where and . The solutions state that and then find , which is a contradiction. They should have and to give .​
  • The resulting equation is better written as so that the term does not appear to be part of the log. Alternatively, it can be written as or as .​
  • For 12(c), the conclusion should be for integers or for .​
  • With q13(b), I wonder if the marking will require a justification that at impact with the wall proves that it has yet to hit the floor...​
  • I am confident that q14(a) is meant to be solved by vectors​
 

tito981

Well-Known Member
Joined
Apr 28, 2020
Messages
326
Location
Orange
Gender
Male
HSC
2021
the wording of the sample size question was so long that i didnt see 'round to the nearest thousand', gonna lose a mark to not rounding imagine that.
 

BAYPALS

Member
Joined
Dec 23, 2018
Messages
34
Gender
Male
HSC
2020
Looking at the solutions provided above:
  • there is a small error in Q5 where as , but the solution writer has stated that . This is because . Thus, the angle must be obtuse or - the solution writer is correct that NESA have made a mistake in including in the category of "obtuse" angles.
  • In q11(h), though it is not in the syllabus, a potentially simpler solution is:

  • Per the discussion above, q12(a) appears wrong​
  • the handling of the absolute value in q12(b) is wrong as the temperature is increasing towards 25, hence and the equation is where and . The solutions state that and then find , which is a contradiction. They should have and to give .​
  • The resulting equation is better written as so that the term does not appear to be part of the log. Alternatively, it can be written as or as .​
  • For 12(c), the conclusion should be for integers or for .​
  • With q13(b), I wonder if the marking will require a justification that at impact with the wall proves that it has yet to hit the floor...​
  • I am confident that q14(a) is meant to be solved by vectors​
Im confused. Is Q12A going up the correct solutions (always above x axis) or going down (below x axis)? which one is the correct answer
 

CM_Tutor

Moderator
Moderator
Joined
Mar 11, 2004
Messages
2,644
Gender
Male
HSC
N/A
Im confused. Is Q12A going up the correct solutions (always above x axis) or going down (below x axis)? which one is the correct answer
Assuming that the slope field posted elsewhere in this thread is accurate, the path will have a minimum stationary point and always be above the -axis
 

notme123

Well-Known Member
Joined
Apr 14, 2020
Messages
1,002
Gender
Male
HSC
2021
can you still get a scaled mark of 100 if you didnt get 100%? e.g. 69.5 or 69/70
 

icycledough

Well-Known Member
Joined
Aug 5, 2021
Messages
783
Gender
Male
HSC
2020
can you still get a scaled mark of 100 if you didnt get 100%? e.g. 69.5 or 69/70
Just for clarification, I believe there is no half marks awarded in the HSC, but someone can let me know if they do in fact provide half marks.
 

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,110
Gender
Male
HSC
2006
Just for clarification, I believe there is no half marks awarded in the HSC, but someone can let me know if they do in fact provide half marks.
Converting a mark out of 70 into a mark out of 100 will lead to decimal places.
 

notme123

Well-Known Member
Joined
Apr 14, 2020
Messages
1,002
Gender
Male
HSC
2021
Just for clarification, I believe there is no half marks awarded in the HSC, but someone can let me know if they do in fact provide half marks.
its true, my english tutor got half marks for mod c and unseen but idk for maths. probs not.

so you basically get no returns from scaling if you get 69/70. well a 69 is like a 98.6% or something which rounds to 99 ig
 

icycledough

Well-Known Member
Joined
Aug 5, 2021
Messages
783
Gender
Male
HSC
2020
Like for example, if there was a 1 mark question in a maths exam (not MC), then you would either get 0 or 1 for it; half marks aren't actually awarded in the marking of the exam. Obviously, the percentage conversion will be decimals (like if you get 67,68,69), but the raw mark will be a whole number. I was saying this as for internals for a language I did last year (which involved translation into English), our teacher would deduct a quarter mark for every mistake.
 

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,110
Gender
Male
HSC
2006
A bit out of order.

I've reordered it.

Also part of 12a is missing (direction field on writing paper)

EDIT: 12a picture is here (thanks to pokipoki beanz):

View attachment 33972
Just realised the x and y axes are differently orientated. Is that a typo? Or is that deliberate?
 

tywebb

dangerman
Joined
Dec 7, 2003
Messages
1,712
Gender
Undisclosed
HSC
N/A
Just realised the x and y axes are differently orientated. Is that a typo? Or is that deliberate?
It is not specified in the question that y is a function of x or vice versa. I agree that it's a bit strange. But I don't think it makes any difference.
 

tywebb

dangerman
Joined
Dec 7, 2003
Messages
1,712
Gender
Undisclosed
HSC
N/A
Last edited:

notme123

Well-Known Member
Joined
Apr 14, 2020
Messages
1,002
Gender
Male
HSC
2021
for that sample proportion q was it even important that it was less than 2.5?? because every solution ive seen so far doesnt use that fact. i think the z score has to be greater than 2.
 

tito981

Well-Known Member
Joined
Apr 28, 2020
Messages
326
Location
Orange
Gender
Male
HSC
2021
for that sample proportion q was it even important that it was less than 2.5?? because every solution ive seen so far doesnt use that fact. i think the z score has to be greater than 2.
it is important that its less than 2.5, because the question states that 'the sample size is chosen so that the chance of shutting down the machine unnecessarily is less than 2.5%'. So this means since you use z=2, the upper 2.5% will never cause the machine to shut down because it is at the upper end where the machine will never shut down. This is because when you think about p, you want the machine to be in the upper 2.5% because that means it is working to near perfect standard.
 

CM_Tutor

Moderator
Moderator
Joined
Mar 11, 2004
Messages
2,644
Gender
Male
HSC
N/A
I doubt it. Here are another set of solutions, by Nash. And you can see they used the same diagram in 12a.
Nash's solution is missing the sketch in q12(d)(iii) and has the sane problem as the other solution in handling the absolute value in q12(b). It does use the vector approach that I believe was sought in q14(a), though.
 

Siwel

Active Member
Joined
Aug 21, 2021
Messages
208
Gender
Male
HSC
2021
Nash's solution is missing the sketch in q12(d)(iii) and has the sane problem as the other solution in handling the absolute value in q12(b). It does use the vector approach that I believe was sought in q14(a), though.
what about q13a) why is it square root y? thought it should just be y
 

CM_Tutor

Moderator
Moderator
Joined
Mar 11, 2004
Messages
2,644
Gender
Male
HSC
N/A
what about q13a) why is it square root y? thought it should just be y
You are correct, and well caught! Nash's solution to q13(a) is indeed incorrect. The solutions posted earlier answered this question correctly. Volumes rotated about the y-axis are indeed of the form


which, in this case of one volume subtracted from another, gives

 

Users Who Are Viewing This Thread (Users: 0, Guests: 2)

Top