***2015 LC Maths Paper 2 - Higher Level - June 8th***

Kremin

Luke Armstrong wrote: »

Wait for Q1 you were supposed to put W or L right? not 1,1

I really ****ing hope so, why else would they tell you a success is W and a loss is L? I'm glad I'm not the only one who assumed that -_-

Also actually, they had already filled two boxes in with W and L, so I'm sure we're right.

RoRo979

qweerty wrote: »

Okay, okay, there's probably a good argument for me to remove the link. Problem is it's been reposted by a few!

Just to totally clarify, I have no connection with the person or company who produced the "solutions"; I just saw the link for it on someone's FB.

dont worry were not lashing out at you just all get a bit scared when the answer we see is different to what we previously thought was right

skippy1977

simplyno1 wrote: »

Skippy would you mind saying the answer to 2. b, 2.c, 7.c, 7.d? you dont have to do it out, just an explanation of some sort.

For 2(b) I'd have done this.



2 (c)



The format is as outlined by the Project Maths development team...explanation of a p value is tricky and not sure I've fully done it justice but something along those lines.

Again not to be critical of anyone posting solution....I make tonnes of mistakes (probably some in this) but different when a company is trying to sell a product claiming to have the likely questions.

qweerty

F-uck, I'm really sorry that I've caused this uncertainty. Just assume everything in it is wrong!

skippy1977

qweerty wrote: »

F-uck, I'm really sorry that I've caused this uncertainty. Just assume everything in it is wrong!

haha in fairness there was plenty right in it too!!

Peregrine

If you want, I can remove the link and all quotes of the link.

skippy1977

simplyno1 wrote: »

Skippy would you mind saying the answer to 2. b, 2.c, 7.c, 7.d? you dont have to do it out, just an explanation of some sort.

Here is my Q7...there is alot going on so...could be errors! Didn't write out the rectangle+triangle part in the most elegant way but...

DarraghF197

Ugh, I think i might have found an error with that question for me. Firstly, I'm not fully convinced if I used r as 80 for the bigger circle! I was rushing it at the end as I realised I had squared one bit wrong just in time!

Then I might have used the area equation of the circle as the formula that's given for radians, where the area is halved Oh well... Concentrate on French!

randylonghorn

qweerty wrote: »

Just to distance myself from it... They're done by an online grinds company (with which I have no connection).

I know, but they're a particularly bad one too.

Pretty sure they were offering "Predictions for Subject X" at €10 each there a week or two ago.

Leeches.

RoRo979 wrote: »

Tbh i think you should just delete the link because so much mistakes in it will only make people feel worse.

Agreed, I let it sit earlier, but if there are that many mistakes, it's only gonna cause consternation.

simplyno1

cheers skippy. although it just shows me what i got wrong lol. are you a maths teacher or what?! thanks alot!

qweerty

randylonghorn wrote: »

I know, but they're a particularly bad one too.

Pretty sure they were offering "Predictions for Subject X" at €10 each there a week or two ago.

Leeches.

Good call. Would cause you to question the quality of their "products".

Tet2015

A bit off topic, but how many of you guys did higher level maths because you're planning on studying Computer Science?

Luke Armstrong

Tet2015 wrote: »

A bit off topic, but how many of you guys did higher level maths because you're planning on studying Computer Science?

Reason for doing it is I like it/good at it but yes I do plan on studying cs

Tet2015

Luke Armstrong wrote: »

Reason for doing it is I like it/good at it but yes I do plan on studying cs

I feel so intimidated by sheer number of people doing HL math for CS because I too plan on studying it and I feel as if my chances of getting into the colleges at home (UCD & Trinity) have ultimately been reduced as I couldn't do HL math

mayway

Frigating wrote: »

The whole exam. If you get a wrong answer and have to use it for another part of the question (say part a and b) you'll be marked for part b based on your answer for a. As long as your method is right, it's just that value (the answer from a) is wrong, you'll get full marks for b. (though you'll lose marks for part a)

Of course you're hoping that the person correcting your paper is not too lazy or incompetent to work out what the answers would be if they used different input values.......

Luke Armstrong

Tet2015 wrote: »

I feel so intimidated by sheer number of people doing HL math for CS because I too plan on studying it and I feel as if my chances of getting into the colleges at home (UCD & Trinity) have ultimately been reduced as I couldn't do HL math

Just because you do HL maths doesn't automatically mean you're going to get 600 points, I'm hoping for an A1/2 but still struggling for CS UCD.

randylonghorn

mayway wrote: »

Of course you're hoping that the person correcting your paper is not too lazy or incompetent to work out what the answers would be if they used different input values.......

How to spread doom and gloom based on ... well, absolutely nothing at all.

If you can't post constructively, don't post at all, thanks.

Kremin

mayway wrote: »

Of course you're hoping that the person correcting your paper is not too lazy or incompetent to work out what the answers would be if they used different input values.......

I'm sure an examiner will be able to tell a blatantly wrong answer and an answer thats right. Also remember that I'm sure a lot of people will make the same mistake... i.e using r=root365 so the examiner will probably realise the answers based on other peoples work.

Kerrypike

Any chance someone could send me a link of those answers that were taken off? Just curious

dazzadazza

Tet2015 wrote: »

I feel so intimidated by sheer number of people doing HL math for CS because I too plan on studying it and I feel as if my chances of getting into the colleges at home (UCD & Trinity) have ultimately been reduced as I couldn't do HL math

Hey I'm also doing CS in trinity next year. Before now I didn't know anyone else that wanted to do it.

Tet2015

dazzadazza wrote: »

Hey I'm also doing CS in trinity next year. Before now I didn't know anyone else that wanted to do it.

I've always expected CS to be a really popular choice at colleges like TCD and UCD considering the recent increase in value for CS degrees. I'm doing most subjects at HL but maths so I hope I still have a good chance. Anyway, going back on topic, how did you find paper 2 overall compared to past papers?

dazzadazza

Tet2015 wrote: »

I've always expected CS to be a really popular choice at colleges like TCD and UCD considering the recent increase in value for CS degrees. I'm doing most subjects at HL but maths so I hope I still have a good chance. Anyway, going back on topic, how did you find paper 2 overall compared to past papers?

Loved it! I don't like proving things in geometry so I was delighted not to see that come up! Also we had a nice theorem, derivation and construction. And the questions in general were very nice. I'd be disappointed not to get an A even though realistically I'd usually be a B student in maths.

MegLC

Kerrypike wrote: »

Any chance someone could send me a link of those answers that were taken off? Just curious

If you go onto the "leavingcertpredictions.com" facebook page, they have the link up

gammy_knees

Just had a quick look at some of their solutions for Q8. Are parts b,c, d(i) incorrect.
Is part b (.3)(.4)(.6)=.072? Because if he was unsuccessful on his first throw, his prob of success on second throw is 0.6 which means failure for this throw is 0.4.
By this logic are answers to part (c) wrong?

In part d(i) there is no consideration in the answer when calculating P(n+1) whether Pn was a success or failure. So should the answer go like so;
If Pn was a successful throw then P(n+1)=0.8 x Pn and if Pn was an unsuccessful throw then P(n+1) = 0.6 x (1-Pn). Expand to 0.6-0.6Pn
Add the two P(n+1)'s to get 0.8Pn +0.6-0.6Pn which gives the desired 0.6-0.2Pn

DexterXX

gammy_knees wrote: »

Just had a quick look at some of their solutions for Q8. Are parts b,c, d(i) incorrect.
Is part b (.3)(.4)(.6)=.072? Because if he was unsuccessful on his first throw, his prob of success on second throw is 0.6 which means failure for this throw is 0.4.
By this logic are answers to part (c) wrong?

In part d(i) there is no consideration in the answer when calculating P(n+1) whether Pn was a success or failure. So should the answer go like so;
If Pn was a successful throw then P(n+1)=0.8 x Pn and if Pn was an unsuccessful throw then P(n+1) = 0.6 x (1-Pn). Expand to 0.6-0.6Pn
Add the two P(n+1)'s to get 0.8Pn +0.6-0.6Pn which gives the desired 0.6-0.2Pn

Yeah I did that for part d(i) too. Did anyone get 6 for q8 part e(ii)?

gammy_knees

Is Q1(c) in error as well?
Instead of having 10C3 should it not be 9C2 as you are looking for 2 successes from 9 knowing that the 10th throw is to be your third success?

japester

I've gone through both papers at this stage (did my leaving way back but I like to see how I get on each year) and have done what I can of them. I think you're right about Q1(c) on paper 2. I'm coming out with 0.0791 for that correct to 4 d.p. - the probability that there are 2 wins in the first 9 experiments is 9C2 * (13/18)^7 * (5/18)^2 giving 0.284703908 and then the probability that the 3rd win occurs in the 10th experiment will be this number multiplied by (5/18) giving me the 0.0791. Probability was never my favourite though :-)


I also got that for this question. Basically used the fact that term n of geometric sequence is given by a*r^(n-1) and with a = 0.05 and r = (1/5)just set (0.05)*(1/5)^(n-1) < 0.00001 and eventually get n < 6.292 for the inequality. So then the largest value of n must be 6 to keep the inequality true. I was just wondering should the question have said "find the largest value of n" rather than the "smallest" though?

DexterXX

japester wrote: »

I also got that for this question. Basically used the fact that term n of geometric sequence is given by a*r^(n-1) and with a = 0.05 and r = (1/5)just set (0.05)*(1/5)^(n-1) < 0.00001 and eventually get n < 6.292 for the inequality. So then the largest value of n must be 6 to keep the inequality true. I was just wondering should the question have said "find the largest value of n" rather than the "smallest" though?

Just realised the answer is 7. What I think you might have done is forget to change the sign of the inequality when dividing across by ln.2
I said the general formula was ar^n rather than ^n-1

japester

I'm almost 100% sure the nth term of a geometric sequence is given by a*r^(n-1) alright - just checked there online too. Just double checked my calculations again and basically the questions asks to find the smallest value of n such that p-pn < 0.00001. Here p is 0.75 and we know p0 is the probability of success on the first throw which is 0.7. So the first term of the sequence is 0.75-0.7 = 0.05 and we know from part (i) the common ratio is 0.2. So, for me, the general term of the sequence an = p - pn = a*r^(n-1) i.e. (0.05)(0.2)^(n-1) < 0.00001 => (0.2)^(n-1)<0.0002 => (n-1)log(0.2)>log(0.0002) => n-1 > 5.292 => n > 6.292. So I'm now getting n must be 7 as a result alright - you were dead right about having to change the sign of the inequality later on because we're dealing with the logs of numbers less than 1.

As a matter of interest for a test, if you now plug the value n = 7 into the formula (0.05)(0.2)^(n-1) you'll get 0.0000032 which is < 0.00001. When you plug n= 6 in you'll get 0.000016 which is just > 0.00001.

So finally, finally, finally, I think the answer to this part is definitely 7 :-)