ATAR Notes: Forum
Archived Discussion => VCE Exam Discussion 2017 => Results Discussion => Victoria => VCE Maths Exams => Topic started by: Sine on November 08, 2017, 01:11:04 pm
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All solutions are of exam standard and what would be required of the harshest assesor.
Estimated A+ cutoff: 36.5-37.5
NOTE: Whenever I write something like "where a =12" that is not required for full marks but is nice to put in.
EDIT: 8c should not include 0 (Zhen)
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Just wondering why you included p=0, cause I thought that if p=0, then the probablity of A given B and B given A would be 0, cause they would be mutually exclusive events and this contradicts the given information.
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Just wondering why you included p=0, cause I thought that if p=0, then the probablity of A given B and B given A would be 0, cause they would be mutually exclusive events and this contradicts the given information.
yeah you are right my bad. didn't check over ahah
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Hey Sine 😊 For the last pg, I found the gradient of AC through tan45=1. Since AC is perpendicular to BC, I found that the gradient of BC was -1. Is this correct?
Also, when I got the eqns in both c) and d), I let root x=a and I rejected one if the solns since a has to be greater than or equal to 0. Is this right?
For Q4, when I got to your 3rd line of working, I squared both sides. I got the same ans as you at the end. Is this ok?
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Hey Sine 😊 For the last pg, I found the gradient of AC through tan45=1. Since AC is perpendicular to BC, I found that the gradient of BC was -1. Is this correct?
Also, when I got the eqns in both c) and d), I let root x=a and I rejected one if the solns since a has to be greater than or equal to 0. Is this right?
For Q4, when I got to your 3rd line of working, I squared both sides. I got the same ans as you at the end. Is this ok?
yes AC perpendicular to BC to find gradients is fine
not sure what you mean by your second question
for q4 if all the inequalities you wrote down were correct you are fine. The reason I don't like to do anything other than linear tranpositions (stuff like logs and exponentials) over inequalities is because it is much harder to keep track on whether i need to flip the inequality or not.
hope this helps
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jeez that's rough, an A+ cut off around 36-37. What exam score in exam 2 do i need for a 40+? I think i got 33-34/40 for exam 1.
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yes AC perpendicular to BC to find gradients is fine
not sure what you mean by your second question
for q4 if all the inequalities you wrote down were correct you are fine. The reason I don't like to do anything other than linear tranpositions (stuff like logs and exponentials) over inequalities is because it is much harder to keep track on whether i need to flip the inequality or not.
hope this helps
Thanks sine
I meant to say: when I got to -2root x=1-3x in a) and 2rootx=1-3x in b), I rearranged to let the rhs=0. e.g. for part a), I got 3x-2rootx-1=0. I let a=root x, so 3x=a squared and I solved the quadratic eqn.
Then, I rejected one of the solns since a has to be greater than or equal to 0 (a=rootx).
Is that ok?
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jeez that's rough, an A+ cut off around 36-37. What exam score in exam 2 do i need for a 40+? I think i got 33-34/40 for exam 1.
just my estimate :)
last year it was 34/40 and I would've predicted 35-36 so who knows ahah
Aim for 70+/80 and good sacs should secure 40+ you might be able to get away with high 60's/80
Thanks sine
I meant to say: when I got to -2root x=1-3x in a) and 2rootx=1-3x in b), I rearranged to let the rhs=0. e.g. for part a), I got 3x-2rootx-1=0. I let a=root x, so 3x=a squared and I solved the quadratic eqn.
Then, I rejected one of the solns since a has to be greater than or equal to 0 (a=rootx).
Is that ok?
that sounds good, as long as you showed a reason for it not just randomly discarding it you are ok.
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just my estimate :)
last year it was 34/40 and I would've predicted 35-36 so who knows ahah
Aim for 70+/80 and good sacs should secure 40+ you might be able to get away with high 60's/80
that sounds good, as long as you showed a reason for it not just randomly discarding it you are ok.
Thanks again sine 😊
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I'm still salty about that last question. Absolutely horrible...
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I'm still salty about that last questiom. Absolutely horrible...
same here just wanted to check if i would get marks for attempting though
9c,
I worked out M=-1 but was not able to work out C. Is this one mark?
9d,
If i simply wrote let Tangent of AC = Tangent of CB (without working out the tangents) do you guys think thats worth any marks. I also was able to conclude that the tangent of AC occurred at 1/9 and the gradient of the tangent was 1. But did not go further due to the confusion with the graph and domain of the gradient (0,1).
Also thank you so much for your help guys.
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Do any of yous reckon it is possible to get over a 40 is methods with a combined score across both exams of 100/120? Or even with low 30's exam 1 and high 60s-low 70s exam 2?
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question 9d
C coordinates ( 11/27 , 16/27 )
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For question 7B i), wouldn't the answer be -1 as it's asking for the "largest possible value", and -1>-3?
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Range is [0, infinity) not [1,infinity)
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same here just wanted to check if i would get marks for attempting though
9c,
I worked out M=-1 but was not able to work out C. Is this one mark?
9d,
If i simply wrote let Tangent of AC = Tangent of CB (without working out the tangents) do you guys think thats worth any marks. I also was able to conclude that the tangent of AC occurred at 1/9 and the gradient of the tangent was 1. But did not go further due to the confusion with the graph and domain of the gradient (0,1).
Also thank you so much for your help guys.
m=-1 should get you a mark imo
hmm depends how they mark for your 2nd question if heaps don't do well you could get a mark but I wouldn't count on it
Do any of yous reckon it is possible to get over a 40 is methods with a combined score across both exams of 100/120? Or even with low 30's exam 1 and high 60s-low 70s exam 2?
yeah it's possible but you'd want exam 2 to be hard
For question 7B i), wouldn't the answer be -1 as it's asking for the "largest possible value", and -1>-3?
it is true that -1 is a larger number than -3 but the domain given was from - infinity to c.
and we can't go below 0 to a negative number since the range of g must be in the domain of f (which is all positive numbers including 0)
Range is [0, infinity) not [1,infinity)
which question
for the first [1,inifnity) the domain is restricted of f (good trick by vcaa imo)
for the 2nd the min output of g(x) is 0 so the min of f(g(x) = sqrt(0+1) = 1
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for the last question I successfully found the equation of line CB. However in the last part in which we had to find equation of line CA i accidentally subbed the x=1/9 into the gradient rule. And no, due to the confusion of how x=1 is an answer, I did not notice anything fishy till I got home. I then equated both euations of lines to find the x value, I then subbed the x-value into one of the equations and got diffrerent coordinates for C (than the actual ones) due to the wrong equation for CA.
Just wanted to ask would I be deprived of the total 4 marks or would would the accessors award me consequential error marks.
Also what exam 2 mark do I need if I have around 32/40 on exam 1 and want a 35+
Thanks :D :D
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jeez that's rough, an A+ cut off around 36-37. What exam score in exam 2 do i need for a 40+? I think i got 33-34/40 for exam 1.
I'm in the same boat. We'll smash exm 2 tomorrow together bro.
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For question 7B i), wouldn't the answer be -1 as it's asking for the "largest possible value", and -1>-3?
no, because if a was -3 then the range of that function wouldn't be a subset of the domain of the other function
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I'm in the same boat. We'll smash exm 2 tomorrow together bro.
Hopefully :( My mentality is pretty bad right now, coming into today i was expecting high 30s. So many silly mistakes everywhere and can't believe i didn't get the trig question...oh well you cant do anything about it now, just need to smash that exam 2.
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For question 5- if you got part a) wrong and carried through using the same error ((4/5) instead of (3/5) for not logging in), would you get a consequential mark for part b 1-incorrect answer and part c? Right now, I am looking at 33-35/40. What mark would I need in exam 2 to get a study score 43+?
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For question 5- if you got part a) wrong and carried through using the same error ((4/5) instead of (3/5) for not logging in), would you get a consequential mark for part b 1-incorrect answer and part c? Right now, I am looking at 33-35/40. What mark would I need in exam 2 to get a study score 43+?
Well...at least a 77(?) if the exam is hard then maybe 75+
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Well...at least a 77(?) if the exam is hard then maybe 75+
Well I am doomed :( . If it was 39/40, I would have had a better chance., but for some reason it was worse than my practice exams :/
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Well I am doomed :( . If it was 39/40, I would have had a better chance., but for some reason it was worse than my practice exams :/
Haha hey, we're on the same boat here man, and it's still not over just remember to relax tonight, and maybe study for a bit. I'm sure you've studied enough right? :)
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I'm the same, kept telling myself that it can't be 1 for the last question, ended up making up a random number to use as the y-int of BC and am hoping for consequential for the last part and lost 3 marks coz of silly mistakes prior to that.Sitting somewhere between 32-35, so rip 40 =(. I actually want to die, put in so much effort for nothing.
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I'm the same, kept telling myself that it can't be 1 for the last question, ended up making up a random number to use as the y-int of BC and am hoping for consequential for the last part and lost 3 marks coz of silly mistakes prior to that.Sitting somewhere between 32-35, so rip 40 =(. I actually want to die, put in so much effort for nothing.
Same here, I don't even know why I bother with life, I got the last question right, arguably the most difficult, and then I proceeded to lose so many marks on all the other questions :(
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Haha hey, we're on the same boat here man, and it's still not over just remember to relax tonight, and maybe study for a bit. I'm sure you've studied enough right? :)
Done around 6 paper 1 and 6 paper 2 exams. It is really frustrating when the errors made are simple mistakes like 16n = 30000, therefore n must be 16+ 2/3 so n= 17 etc. I guess that's one thing that is significantly less likely to happen when Exam 2 is reliant on the Ti-nspire or Classpad. The rest is down to the last question where only 2% of the population get the correct answer.
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Anyone reckon the hardest question on the exam was recognising that the diagram on the last question was for a general theta and not 45 degrees?
Literally was on track to finish 30mins early but then this bs happened. Couldn't even check my work properly afterwards and full on monkeyed out at least 5 marks for it.
FeelsBadMan.
@samsung, at least you didn't evaluate sqroot(3/16n) as sqrt(3)/4n
:^) I then solved for n and had a sqrt3 which I approximated as 1.7 and simplified from this. I got 43 LMAO.
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Just a query, the last question since (1,0) was an endpoint and hence gradient would be undefined how can you find a tangent. Even if it was defined it clearly was not (1,0) as point B did not intersect with the functions x-intercept. Also if it did, then BC wouldn't be a tangent as it would have intersected the function once at B and again shown on the graph? How can this be explained?
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Just a query, the last question since (1,0) was an endpoint and hence gradient would be undefined how can you find a tangent. Even if it was defined it clearly was not (1,0) as point B did not intersect with the functions x-intercept. Also if it did, then BC wouldn't be a tangent as it would have intersected the function once at B and again shown on the graph? How can this be explained?
Is it possible for the question to be scratched because i just find that the answer contradicts the two pieces of information (the domain and the graph) provided by VCAA?
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I don't think it'll be scratched but they would accept both answers such as if you stated tangent is undefined due to endpoint and intersection of both points, although I might be wrong in my understanding
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For the last question, how many marks out of 4 would we get for just the equation of AC?
I got the equation but then equated it to a wrong equation by accident so I'm only gonna get marks for the equation of AC
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For the last question, how many marks out of 4 would we get for just the equation of AC?
I got the equation but then equated it to a wrong equation by accident so I'm only gonna get marks for the equation of AC
You should get 3 marks, given that you got the right equation for AC, and your working out is all correct. You would only lose a mark for getting the wrong coordinates.
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Really, that would be amazing. Yep I've confirmed that my equation for AC was correct, with proper working out as well :)
Thanks so much
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There's a good chance they could have 1 mark for the correct x-coord and 1 mark for the correct y-coord fr
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Hi guys, a question that seems to be highly contentious at my school, a relatively strong cohort, is whether the final question of the Computer Login probability section was conditional? Many argue, including myself, that because it states "Jac logs on to the computer successfully", that it implies it is a conditional question, very similar to that of one of the questions in the 2012 VCAA Exam, where there was another hidden conditional probability question that only 3% of the state got full marks for (according to the official VCAA Examination Report). So, what we were proposing was that the value obtained from the previous question, which was asking for him to successfully login in entirely, (which was 98/125) would be used in the final question. We saw it as a conditional by saying find the probability that he logs in on the 2nd or 3rd attempt, given that he logs in to the computer successfully (found to be 98/125 in the previous question), as it was stated in this question that 'Jac logs on to the computer successfully". Hence, our method went on to have the answer as (2/5 x 3/5) + (3/5 x 3/5 x 2/5) / (98/125). This gave an answer of 24/49. Although I can also see why it may be 48/125, I believe it is a conditional question. Thanks
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Hi guys, a question that seems to be highly contentious at my school, a relatively strong cohort, is whether the final question of the Computer Login probability section was conditional? Many argue, including myself, that because it states "Jac logs on to the computer successfully", that it implies it is a conditional question, very similar to that of one of the questions in the 2012 VCAA Exam, where there was another hidden conditional probability question that only 3% of the state got full marks for (according to the official VCAA Examination Report). So, what we were proposing was that the value obtained from the previous question, which was asking for him to successfully login in entirely, (which was 98/125) would be used in the final question. We saw it as a conditional by saying find the probability that he logs in on the 2nd or 3rd attempt, given that he logs in to the computer successfully (found to be 98/125 in the previous question), as it was stated in this question that 'Jac logs on to the computer successfully". Hence, our method went on to have the answer as (2/5 x 3/5) + (3/5 x 3/5 x 2/5) / (98/125). This gave an answer of 24/49. Although I can also see why it may be 48/125, I believe it is a conditional question. Thanks
hey this is a valid pretty valid question
2012 question was "daniel recieves telephone calls on both monday and tuesday What is the probability that Daniel receives a total of four calls over these two days?"
2017 question was "Calculate the probability that he logs on to the computer successfully on the 2nd or the third attempt"
so some subtle differences
Hard to explain reasoning other than intuition
itute also has their answers up and they got 48/125 :)
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hey this is a valid pretty valid question
2012 question was "daniel recieves telephone calls on both monday and tuesday What is the probability that Daniel receives a total of four calls over these two days?"
2017 question was "Calculate the probability that he logs on to the computer successfully on the 2nd or the third attempt"
so some subtle differences
Hard to explain reasoning other than intuition
itute also has their answers up and they got 48/125 :)
Thanks for this response! But what also may be subtle hint to further push my case is that the previous question asked "in the form of a/b" being 98/125. With the next question asking about 2nd or 3rd attempt, the question asked "in the form of c/d", meaning they used different constants, instead of saying on "c/b". Although this may essentially give away the denominator's value if it were to be this way (where b = 125), I have seen them use on practice exams the repetition of a constant if it is applicable in multiple stems within a question. Food for thought :)
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Thanks for this response! But what also may be subtle hint to further push my case is that the previous question asked "in the form of a/b" being 98/125. With the next question asking about 2nd or 3rd attempt, the question asked "in the form of c/d", meaning they used different constants, instead of saying on "c/b". Although this may essentially give away the denominator's value if it were to be this way (where b = 125), I have seen them use on practice exams the repetition of a constant if it is applicable in multiple stems within a question. Food for thought :)
two constants can be the same
consider a line in the form y= mx + c it is possible to have a line such that m = c so y =x + 1
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Hi guys, a question that seems to be highly contentious at my school, a relatively strong cohort, is whether the final question of the Computer Login probability section was conditional? Many argue, including myself, that because it states "Jac logs on to the computer successfully", that it implies it is a conditional question, very similar to that of one of the questions in the 2012 VCAA Exam, where there was another hidden conditional probability question that only 3% of the state got full marks for (according to the official VCAA Examination Report). So, what we were proposing was that the value obtained from the previous question, which was asking for him to successfully login in entirely, (which was 98/125) would be used in the final question. We saw it as a conditional by saying find the probability that he logs in on the 2nd or 3rd attempt, given that he logs in to the computer successfully (found to be 98/125 in the previous question), as it was stated in this question that 'Jac logs on to the computer successfully". Hence, our method went on to have the answer as (2/5 x 3/5) + (3/5 x 3/5 x 2/5) / (98/125). This gave an answer of 24/49. Although I can also see why it may be 48/125, I believe it is a conditional question. Thanks
Unfortunately for you, this won't be the case. We need to consider whether the universal set has indeed been reduced.
In this entire question, there are 4 total possibilities:
Jac logs in on the 1st attempt
Jac logs in on the 2nd attempt
Jac logs in on the 3rd attempt
Jac fails to log in
There is nothing in this question to indicate that none of these are possible any more.
Consider a similar scenario:
A plays B in a best of 5 sets game of tennis.
Find the probability that A beats B in 3 or 4 sets.
A simplified universal set is:
{A wins in 3 sets, A wins in 4 sets, A wins in 5 sets, A does not win}
The probability that we are looking for is obtained by finding:
Pr(A wins in 3 sets) + Pr(A wins in 4 sets)/(Pr(A wins in 3 sets) + Pr(A wins in 4 sets) + Pr(A wins in 5 sets) + Pr(A loses))
= Pr(A wins in 3 sets) + Pr (A wins in 4 sets)
The bolded question above asks us to find the probability that A beats B in some way, but doesn't indicate that A DEFINITELY beats B, hence there is no condition to consider.
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Unfortunately for you, this won't be the case. We need to consider whether the universal set has indeed been reduced.
In this entire question, there are 4 total possibilities:
Jac logs in on the 1st attempt
Jac logs in on the 2nd attempt
Jac logs in on the 3rd attempt
Jac fails to log in
There is nothing in this question to indicate that none of these are possible any more.
Consider a similar scenario:
A plays B in a best of 5 sets game of tennis.
Find the probability that A beats B in 3 or 4 sets.
A simplified universal set is:
{A wins in 3 sets, A wins in 4 sets, A wins in 5 sets, A does not win}
The probability that we are looking for is obtained by finding:
Pr(A wins in 3 sets) + Pr(A wins in 4 sets)/(Pr(A wins in 3 sets) + Pr(A wins in 4 sets) + Pr(A wins in 5 sets) + Pr(A loses))
= Pr(A wins in 3 sets) + Pr (A wins in 4 sets)
The bolded question above asks us to find the probability that A beats B in some way, but doesn't indicate that A DEFINITELY beats B, hence there is no condition to consider.
‘Jac fails to log in’ can be ruled out, as the question states ‘he successfully logs in’ - hence my reasoning why the set is reduced from 125/125 to 98/125? Or is there a better way you could explain why this isn’t the case? I’m just asking out of genuine curiosity now
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good questions ;D ;D
It would be conditional if the question would say something like "Jac sucessfully logs in...find the probability that is on the 2nd or 3rd attempt"
but the question says "calculate the probability that he logs on to the computer successfully on the 2nd or the third attempt"
the quesiton merely asks for the PROBABILITY that it occurs and probaility is inherently = (success/ success + failures)
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‘Jac fails to log in’ can be ruled out, as the question states ‘he successfully logs in’ - hence my reasoning why the set is reduced from 125/125 to 98/125? Or is there a better way you could explain why this isn’t the case? I’m just asking out of genuine curiosity now
Further to Sine's comment, if you compare to the other example I gave above, my question stated "Find the probability that A beats B..." however, this isn't an indication that A does indeed beat B.
I guess one other way to think about it is to try and describe, qualitatively, the probability required in a different way.
If we want to find the probability of Jac logging on successfully on the 2nd or 3rd attempt out of the entirety of the universal set, is there a different way that we could describe it?
I can't think of anything better or more concise than what was asked on the exam, however, it is quite easy to think of a way of rephrasing it to force a conditional (by making this condition fairly obvious, similar to Sine's description above).