**HL Maths P2 Before/After

DepoProvera

Dapics wrote: »

Thats a very unfair statement.

The fact is that if you feel you wont get your A1 because of that paper then perhaps you dont deserve the A1/ are not a maths genius.
Its all good being able to recognise twists in questions and then subsequently act on them.

But This years course truly teaches true maths.
It teaches the logic behind certain parts of maths.
This is good. I would think any student who wants to do maths in college would greatly appreciate this course.

A grand neighbour of mine, one of the smartest men in the country, an absolute maths genius who programs software for I.T companies said it was a truly good paper in that he would have loved to be doing it.

Just my take on your statement, dont mean to come across two strong

I'd love to know your background, from where you get to decide what 'true maths' is. Statements like this aren't helping. Perhaps if you came out with everything right(clearly you didn't) you could make these sweeping statements, but alas :pac:

Your neighbor's opinion on the paper doesn't have any real bearing on it by the way.

Also it's too, not two. hope this helps

Tankosaur

Mista wrote: »

Cant really remember, but Q4 i said must be independent events, and then just did bernoulli.. for the last one, get prob. of 1 shot in 4 and multiply by 0.6

bernoulli.... boom headshot.

Also for the batteries did people get something like 124 batteries rejected the first time, then 224 the second time and the % increase was somehting like 94% ??

Mista

cocopopsxx wrote: »

I never put it i'n either :eek:

I'd say at this rate, a lot of people didn't.. they wont void all your papers Our class only knew because our examiner said it, if she didn't then I'd never have seen it.

SellingJuan

SD021 wrote: »

I never claimed to be a genius, far from it actually. But I still strongly disagree with you. Mathematical Sciences in UCC is my first choice and has been all year. I do Applied Maths and Physics and yet I still loath this course. To be honest when I think of "True maths" directions of causality and such don't spring to mind.

|"Causality" and such is a very big part of maths... Especially when it comes to applying it in the "real world".

gethepoints

In what way would question 7 be marked? Would the first 5 diagram qs be worth 5 marks each @ 25 marks total and the last 2 questions be 50 marks?

DepoProvera

SellingJuan wrote: »

|"Causality" and such is a very big part of maths... Especially when it comes to applying it in the "real world".

Yeah, causality is an important part of stats, but I don't think I've ever heard 'direction of causality'... Perhaps they wanted us to make an educated guess? My answer seems pretty alright from google anyways but oh well

Tankosaur

SellingJuan wrote: »

|"Causality" and such is a very big part of maths... Especially when it comes to applying it in the "real world".

May I ask what that whole question on direction of causality meant?

I just wrote some crap about the correlation being positive....

Random_Person

To anyone worrying about paper 2 thinking it went bad, don't.

There's a high up maths teacher on the radio saying how it was a crazy paper, things not on the syllabus, things authors of maths books had NEVER heard of.
He also said this: "The paper WILL be marked extremely sympathetically".

I feel so much better after listening

SP534

cocopopsxx wrote: »

I never put it i'n either :eek:

Hmm I think going by this... http://www.boards.ie/vbulletin/showthread.php?t=2055937371 ...We should be safe enough I'd say? Fingers crossed sure, nowt we can do about it now :rolleyes:

hamal

Tankosaur wrote: »

bernoulli.... boom headshot.

Also for the batteries did people get something like 124 batteries rejected the first time, then 224 the second time and the % increase was somehting like 94% ??

yeh i did that but i forgot to say the percentage increase was 94, i said it just increased by 1.2 % or somethin, probly only lose bout 2/3 marks

kaet

Dapics wrote: »

Yeah, Fair enough. I'm not trying to put people down. Fact is i will prob only get a B3 cause i messed up so bad in paper 1.

I'd say everyone is ok. I think the marking schemes for project maths are very broad so the examiners will take a lot of things into account. All in all, everything will run its course.

Just by curiosity...

For Q4. Did anyone get something like a 300 percent increase in batteries?

Allow me to explain:

If i remember correctly, i think there was a huge twist in that question.
The twist was that the mm for the difference thingy (cant remember) were an extra decimal place than the mean.

I converted to meter's and got this:

0.020-0.00025.

(0.25 of 0.020 is 0.00025)
I just subtracted and divided by standard deviation. I got something like 17.5 and then just multiplied it by 10000

Could anyone shed some light on that question?
I found it very confusing.

Didn't think it was a twist, maybe I'm way off here but I just went as normal..

Mean = 20
Std. Dev. = 0.1
X = 19.75 and 20.25

Converted those to Z scores got -2.5 and 2.5 then using table got 0.62% for both and multiplied by two to get 1.24%
10000 x 1.24% = 124 batteries rejected

For the second used the Empirical Rule; as in now that the mean is 20.05mm two standard deviations each side of the mean allows for the 0.25mm error and is 95% within the deviations.
=> 5% rejection rate

5% - 1.24% = 3.76%

Too simplified or did anyone else do something similar?

sdiff

Tankosaur wrote: »

May I ask what that whole question on direction of causality meant?

I just wrote some crap about the correlation being positive....

I just said that the direction of causality was basically saying which variable caused the other. In the case of ours, was higher arrears causing higher interest rates, or the other way around?

Dapics

kaet wrote: »

Didn't think it was a twist, maybe I'm way off here but I just went as normal..

Mean = 20
Std. Dev. = 0.1
X = 19.75 and 20.25

Converted those to Z scores got -2.5 and 2.5 then using table got 0.62% for both and multiplied by two to get 1.24%
10000 x 1.24% = 124 batteries rejected

For the second used the Empirical Rule; as in now that the mean is 20.05mm two standard deviations each side of the mean allows for the 0.25mm error and is 95% within the deviations.
=> 5% rejection rate

5% - 1.24% = 3.76%

Too simplified or did anyone else do something similar?

That seems to be the solution

My mate did that and got that.

Well done man, wasnt an easy question as far as normal distribution questions go. I had never seen a question that hard anywhere based on z scores and normal distributions.

I suppose it isn't a hard question, but its hard to understand

Fair Dues

hamal

kaet wrote: »

Didn't think it was a twist, maybe I'm way off here but I just went as normal..

Mean = 20
Std. Dev. = 0.1
X = 19.75 and 20.25

Converted those to Z scores got -2.5 and 2.5 then using table got 0.62% for both and multiplied by two to get 1.24%
10000 x 1.24% = 124 batteries rejected

For the second used the Empirical Rule; as in now that the mean is 20.05mm two standard deviations each side of the mean allows for the 0.25mm error and is 95% within the deviations.
=> 5% rejection rate

5% - 1.24% = 3.76%

Too simplified or did anyone else do something similar?

Your second part is wrong cause there's three standard deviations to the left of the mean and two to the right

tanzy

Dapics wrote: »

My Method

I was rushing so i know my end value is wrong.

I just used x + y =1.
I brought across x and let it equal to 1-y.
I also did it out a second time and brought across y and let it equal to x-1

I then subbed x and y into general equation and found centre.

With centre i found radius.

Now we know that both lines are parrelel, therefore it is safe to assume we can use the centre and radius derived from the x + y = 1 equation and use it to find perpendicular distance to line x + 2k

I found perpendicular distance from centre to line and let it equal to radius.
I got radius 5 and centre (4,4) by the way.
I squared both sides and solved for k.

I made a mistake in there somewhere but this is the method I used. I think its correct, it certainly makes sense to me.

What a few boyo's did was find where the two lines hit the x-axis.
Then they found distance between two points and subsequently found k to be 5.
Now i dont know whether this is a proper way to answer question. Yet i would think it is, due to the fact that it makes some sense to a certain degree but i dont think it's the right method for the given question

The circle had the y-axis and the x-axis as tangents. Therefore having the radius as 5 and centre as (4,4) would be incorrect. This is how i did it
Step 1: got the obtuse angle of the line x+y=1 and the axis.. 135 degrees
Step 2: i bisected this to get 67.5 degrees and got a value of the slope using tan
Step 3: made an linear equation using this slope and the point (1,0)
Step 4: as the circle touches the x and y axis a linear equation of x=y would pass through the centre
Step 5: i equated the two equations in step 3 and 4 to find the centre
Step 6: i got the equation of the circle (had radius as the x/y value from coc)
Step 7: Equated this with the equation x=y to find the two points where they intersect. One point being the first line x+y=1 and the other point on second equation
Step 8: i made an equation using this point and the slope of -1
Step 9: found the value of k from this and got 5.828 or 3+2root2

Dapics

tanzy wrote: »

The circle had the y-axis and the x-axis as tangents. Therefore having the radius as 5 and centre as (4,4) would be incorrect. This is how i did it
Step 1: got the obtuse angle of the line x+y=1 and the axis.. 135 degrees
Step 2: i bisected this to get 67.5 degrees and got a value of the slope using tan
Step 3: made an linear equation using this slope and the point (1,0)
Step 4: as the circle touches the x and y axis a linear equation of x=y would pass through the centre
Step 5: i equated the two equations in step 3 and 4 to find the centre
Step 6: i got the equation of the circle (had radius as the x/y value from coc)
Step 7: Equated this with the equation x=y to find the two points where they intersect. One point being the first line x+y=1 and the other point on second equation
Step 8: i made an equation using this point and the slope of -1
Step 9: found the value of k from this and got 5.828 or 3+2root2

I had a radius of square root 5.

Your way seems correct, wish I had seen it like that.
I would hope it is marked easy, almost no one in my year got it.

Hayezer

Lads you think theyl be nice enough with attempt marks?

sdiff

kaet wrote: »

Didn't think it was a twist, maybe I'm way off here but I just went as normal..

Mean = 20
Std. Dev. = 0.1
X = 19.75 and 20.25

Converted those to Z scores got -2.5 and 2.5 then using table got 0.62% for both and multiplied by two to get 1.24%
10000 x 1.24% = 124 batteries rejected

For the second used the Empirical Rule; as in now that the mean is 20.05mm two standard deviations each side of the mean allows for the 0.25mm error and is 95% within the deviations.
=> 5% rejection rate

5% - 1.24% = 3.76%

Too simplified or did anyone else do something similar?

I got the same for the first bit (124 batteries).
I'm not sure where you're getting the second bit from. The range is still 20.25 and 19.75. Standardising gave us (20.25-20.05/0.1) and (19.75-20.05/0.1).
If it were 95% (ie 2 standard deviations) it would have to be 0.2 either side of 20, I.e from 19.8 to 20.2

sdiff

tanzy wrote: »

The circle had the y-axis and the x-axis as tangents. Therefore having the radius as 5 and centre as (4,4) would be incorrect. This is how i did it
Step 1: got the obtuse angle of the line x+y=1 and the axis.. 135 degrees
Step 2: i bisected this to get 67.5 degrees and got a value of the slope using tan
Step 3: made an linear equation using this slope and the point (1,0)
Step 4: as the circle touches the x and y axis a linear equation of x=y would pass through the centre
Step 5: i equated the two equations in step 3 and 4 to find the centre
Step 6: i got the equation of the circle (had radius as the x/y value from coc)
Step 7: Equated this with the equation x=y to find the two points where they intersect. One point being the first line x+y=1 and the other point on second equation
Step 8: i made an equation using this point and the slope of -1
Step 9: found the value of k from this and got 5.828 or 3+2root2

Same answer, different method. Used perpendicular distance formula, from each tangent to the centre = radius.

ehshup

sdiff wrote: »

Same answer, different method. Used perpendicular distance formula, from each tangent to the centre = radius.

I think i got the same answer, 5.8etc.... so thank god, when I got that value i thought it must be wrong because i didnt see why they'd give us 2k if it was anything but a whole number

kaet

hamal wrote: »

Your second part is wrong cause there's three standard deviations to the left of the mean and two to the right

Oh yeah, balls. Knew it was too good to be true..

finality

Tankosaur wrote: »

bernoulli.... boom headshot.

Also for the batteries did people get something like 124 batteries rejected the first time, then 224 the second time and the % increase was somehting like 94% ??

I got something like that yeah.

It's wrong though, that's the increase in the NUMBER of batteries rejected, as opposed to the rate. I'd say we'll get almost full marks for it though.

Tankosaur

hamal wrote: »

Your second part is wrong cause there's three standard deviations to the left of the mean and two to the right

Reading that sentence filled me with so much joy......

Tankosaur

finality wrote: »

I got something like that yeah.

Cool I completely ballsed up both 3 and 8 so I need to get as many marks in the rest as possible.

finality

Tankosaur wrote: »

Cool I completely ballsed up both 3 and 8 so I need to get as many marks in the rest as possible.

see my edit? I'd imagine we'd get something like 22/25 though. I ballsed up 8 as well, and one or two others.

Tankosaur

hamal wrote: »

yeh i did that but i forgot to say the percentage increase was 94, i said it just increased by 1.2 % or somethin, probly only lose bout 2/3 marks

The question was vague.

The second part mean there was about 230 or so more rejections. Which is 2.3% rejection. Where as the first part was 1.24% rejection or something like that. So the % increas was 0.9 or something aong those lines.

The other meaning of % percentage increase could be the (number from the second rejection- the number from the first rejection / the number of the first rejection) which comes to 94 %

Tankosaur

finality wrote: »

see my edit? I'd imagine we'd get something like 22/25 though. I ballsed up 8 as well, and one or two others.

Just saw it there. I wrote both answers because I knew the question was vague.


I'm hoping for 25 marks in the first 6 bar 3, maybe 10/15 in that.

Then at least 70 in 7 and about 55 in 8.

That way I can still get my a1 as I did a good paper 1.

reznov

At least it's unpredictable. :cool:

hamal

Tankosaur wrote: »

The question was vague.

The second part mean there was about 230 or so more rejections. Which is 2.3% rejection. Where as the first part was 1.24% rejection or something like that. So the % increas was 0.9 or something aong those lines.

The other meaning of % percentage increase could be the (number from the second rejection- the number from the first rejection / the number of the first rejection) which comes to 94 %

Yeh i did the first one there, most of it right anyway.. hopefully got on alright.. may forget about it now and start studyin irish!

finality

Tankosaur wrote: »

Just saw it there. I wrote both answers because I knew the question was vague.


I'm hoping for 25 marks in the first 6 bar 3, maybe 10/15 in that.

Then at least 70 in 7 and about 55 in 8.

That way I can still get my a1 as I did a good paper 1.

I'd say I got full marks in 3 questions, about 18-22/25 in two and about 12 in one. Then hopefully 75 in 7, and about 40 or so in 8...it was that bad. Which means I may scrape an A2 if I'm lucky, think I got about 90% in paper 1... it just all went wrong More likely is a B though. I'm actually so upset because there was nothing I didn't know how to do, the pressure just got to me.