# CSSA trial (advanced/ extension maths) (1 Viewer)

#### synthesisFR

##### Well-Known Member
wait did the 2023 paper have a phillips lightbulb question?

#### tywebb

##### dangerman
I also used Cramer’s rule and the Moore-Penrose inverse to solve some of them.

These are out-of-syllabus methods, but somewhat superior.

The syllabus methods would be solving equations simultaneously and using the calculator for line of best fit.

So why would Cramer’s rule and the Moore-Penrose inverse methods be superior?

In the case of Cramer’s rule you get the answer in 1 step as opposed to many steps with solving simultaneous equations.

In the case of the Moore-Penrose inverse again you get the answer in 1 step but also it gives the exact line of best fit making subsequent calculations more accurate.

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#### tywebb

##### dangerman
no way in hell is any adv student gonna use this
I would think most adv students are not in hell and so can use it.

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#### tywebb

##### dangerman
Thanks for the photo. It made me realise there is a typo. The p should be a P.

I updated the file and now it looks like this

#### tywebb

##### dangerman
you don't know about matrices?! the hsc is in like two weeks, learn all about them you need it!!
It's pretty easy. You can learn it in 5 minutes. You won't need two weeks.

Many years ago it was actually in the year 10 syllabus!

#### synthesisFR

##### Well-Known Member
It's pretty easy. You can learn it in 5 minutes. You won't need two weeks.

Many years ago it was actually in the year 10 syllabus!
my tutor did say each generation is getting dumber (with more explicit language)

#### its_ace21

##### /æɪs/
my tutor did say each generation is getting dumber (with more explicit language)
now i want to know exactly what he said

#### synthesisFR

##### Well-Known Member
now i want to know exactly what he said
damn it i should have compiled a list of all the outta pocket stuff he said over the two years

#### ZakaryJayNicholls

##### Active Member
i don't even know
Possibly to give you 3x20c pieces if they were low/out of 50c and 10c pieces.
This is not an uncommon thing which people do in sales to prevent themselves from having to rebalance a till.

#### tywebb

##### dangerman
There were no professors. Only 1 of them is a uni lecturer and he was not even the convenor. The other 4 are from high schools.

It s not impossible. Here are my solutions: https://4unitmaths.com/cssa2023adv-tywebb.pdf
CSSA's answer to their 2023 Adv paper Q28b is wrong. They should have checked ln(16/9)-1 is negative and so the distance is ln(9/16)+1 (or written as ln(9/16) - -1 as question said to write it as ln(a/b)-c)

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#### carrotsss

##### New Member
CSSA's answer to their 2023 Adv paper Q28b is wrong. They should have checked ln(16/9)-1 is negative and so the distance is ln(9/16)+1 (or written as ln(9/16) - -1 as question said to write it as ln(a/b)-c)

Checking doesn't seem to be CSSA's strong point because in the CSSA solutions for their 2023 Ext.2 paper Q16c there are actually 2 answers 219.1m/s OR 223.5m/s. They arise from the equation
View attachment 39610
In CSSA's solution the absolute value blissfully disappears and then they only get 1 answer 219.1m/s.

I was not so careless and put my solutions here for comparison and you will see how I got the 2 solutions: https://4unitmaths.com/cssa2023e2-tywebb.pdf
cssa seem to have a tendency of giving dodgy solutions, they have lots of problems in chemistry and physics as well

#### tywebb

##### dangerman
cssa seem to have a tendency of giving dodgy solutions, they have lots of problems in chemistry and physics as well
If the markers are made aware of this before they mark it then it won't matter.

But are they?

If not then dodgy solutions = dodgy marks.

Even worse - if some are made aware of it and others aren't, not only are the marks dodgy, but unfair as well, eg., some students getting marks and other students losing marks - for the same answer!

#### tywebb

##### dangerman
I also put up my solutions to the Ext. 2 CSSA 2023 at https://4unitmaths.com/cssa2023e2-tywebb.pdf

I used an out-of syllabus method for question 12aii choosing 3 planes out of 6 to find the point of intersection of the 2 lines using a matrix equation. This turned it into a question about the intersection of 3 planes having the same point of intersection as the 2 lines.

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#### tywebb

##### dangerman
Also my solutions to the Ext. 1 CSSA 2023 are at https://4unitmaths.com/cssa2023e1-tywebb.pdf

Note in 14a for the extension 1 I used the regularised incomplete beta function, which although outside the syllabus, gets the answer much quicker.

Furthermore use of the complementary error function instead of the table gives a more accurate answer.

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#### Luukas

##### New Member
It is not impossible. Here are my solutions ...
May I ask why you put expenses as 200 + 20n in Q23? Doesn't that make the expenses in the first week 220? The question says that they start at 200 and then increase by 20 per week.

#### Luukas

##### New Member
If you were taught properly you would not feel so bad about it.
This comment is very similar to what I hear the teacher who led the writing team has been saying to his class - and that he feels sorry for students who have teachers complaining that the exam was too difficult...

##### done hsc yay
Anyone know what the averages and top marks were for the CSSA math advanced 2023 trial in different schools

#### its_ace21

##### /æɪs/
my school the average was in the high 60's and ppl got in the 80's and maybe 90's