4 (c) Probability (2 Viewers)

[Loz_metalhead]

I'm so glad I got these right(I think) I did without replacement.

I spent ages trying to figure out how to do probability...my teacher and the textbook we used at school both sucked.

 

[sando]

so because i stuffed up and said replacement... cant believe i changed my mind grrr

will i get any marks ? e.g. CFPA

 

[Amish27]

i think so, they do it in physics, dont see why this should be any different.
And if you still had your other working you might get it all right....markers look for the correct working....something to do with accounting for stress, well the do it in business...not sure bout maths though
Just know the markers is looking to give you marks, not take them away...theyre all nice people...otherwise i fail my hsc

 

[markus123456789]

Your pretty close.

ii.) 10/42 is correct but can be simplified to 5/21, so lets hope the marker isn't a prick and gives you the mark, as some people are fussy about these things.

iii.) P(Of three square chosen are different colour) = 1 - P(Three squares the same colour)

Therefore: 1 - 5/21 (from part ii.)

= 16/21

That's at least what I put, and I've seen a few others with the same answer.

Yeh thats what i got, but it was a bit of a controversial Q i dunno.. it wasnt very specific about if she chose them and them put them back .. or what not.. ^o).. ohwell... i guessed right

 

[meg_1_2_3_4_5]

its gotta be with replacement bcos u cant exactly take away a square on a chessboard. its saying that she just picks a square on a chessboard randomly and then chooses another not at the same time so therefore there still is a chance she'll pick the same one again. its not a chessboard if it only has 62 or 63 squares...

 

[kerfuffle]

Maybe she wanted to put chess pieces or somethng on the chessboard. If that were so, then there's no replacement.
If they wanted replacement, wouldn't the question have told us so? O.O

 

[princessemmie11]

does anyone know wen the answers will be released?? do we have to wait until next year???

 

[meg_1_2_3_4_5]

Maybe she wanted to put chess pieces or somethng on the chessboard. If that were so, then there's no replacement.
If they wanted replacement, wouldn't the question have told us so? O.O

wouldn't they have told us if she wanted to put chess pieces on the board??, but funnily enough nothing about pieces was mentioned.....
Y would they say if its replacement but not say if it wasnt?
All the maths teachers at my school agree that it is replacement because
(a) you cant 'remove' the squares
(b) it implies that the squares are chosen at different times, if however it said that they were chosen simultaneously then it wouldn't be replacement
(c) it sounds like u got it wrong and ur in denial so ur just trying to make urself feel better by adding parts to the question and blaming it on the examiners

 

[4DOGS]

its gota be without replacement otherwise they would of stated. they cant exactly assume that you know if the squares are on a chessboard can be moved coz its not in the syllabus!

 

[kerfuffle]

wouldn't they have told us if she wanted to put chess pieces on the board??, but funnily enough nothing about pieces was mentioned.....
Y would they say if its replacement but not say if it wasnt?
All the maths teachers at my school agree that it is replacement because
(a) you cant 'remove' the squares
(b) it implies that the squares are chosen at different times, if however it said that they were chosen simultaneously then it wouldn't be replacement
(c) it sounds like u got it wrong and ur in denial so ur just trying to make urself feel better by adding parts to the question and blaming it on the examiners

Did I ever say that the question should be blamed on the examiners? No. I don't know anymore than you do why she was picking random squares, so I assumed she wanted to put chess pieces or something on it. I agree with 4DOGS about the 'usually state if it's replacement or not' part. The questions that want replacement usually ask for it in the question.
And I mustn't have gotten it wrong (assuming that it was without replacement), 'cause I got the same answer as H.A.L. And if I do get it wrong, not much I can do about it.
And I don't think I'm in denial, thanks.

 

[StYlez-]

freak, its a chessboard. its just some dikhead picking random squares, why would it get taken away

i got:
a) P(WWW) = 1/2 X 1/2 X 1/2
= 1/8

b) P (WWW) + P(BBB) = 1/4

c) 1- 1/4 = 3/4.

end of story.

 

[cazza.]

mhm i agree with stylez, thats exactly what i got coz why would u take away squares on a chess board??? .....but my teacher said that was wrong....

 

[sando]

yeh i did it that way.. but it said different squares.. just admit it like i did.. we are wrong.


all i am concerned about now.. is will i get ZERO for that whole 4 mark question ?

 

[cazza.]

hahaha yeh we r wrong. i just hope we get even one mark for effort lol

 

[Cabrello]

I did a tree diagram, if the working out is there, i think the teachers would take into account it was a horribly worded question

 

[the pospinator]

man i hate this question, its like that CD question in the catholic trials, its a bit ambiguous

anyway, i think i got it wrong, oh well, working out hopefully will get marks

 

[thehootman]

The only thing that consistantly seems to bring me down is probability. I am terrible at it. I cant even remember my answers and I am assuming in my mark guessing that i got it all wrong. It and shitty geometry crap are my only weak areas:mad1:

 

[Tim035]

3 different squares... ahh shit.
So the first time was 1/2 but then 2nd time was 31/63 as was third time she chose a square.

Alrighty I'll just add this to the growing list of things I COMPLETLY bombed due to exam stress:
2c
3a(iii) (iv)
4a(iii) b, c (ohh thats going to be a lovely mark )
5b(ii)
6a(iii)
7b(ii) (iii)
8a(iv) b(ii)
9c
10b

I estimated 90/120 as my mark when I first left the exam. From stupid errors, rushing and not thinking I'm almost sure it will be as low as 72/120. So band 3 for me in maths, fucken terrific why did I even bother doing the fucken hsc god dam it. I'm sure I could've done 1/1000 of the study I did constantly through out the year for maths and probably still gotten the same mark I'm going to get. Such Such bullshit ....

 

[sanjay_88]

When u choose 3 random squares on a chess board, it's not like u can cut those squares out and then have less of any colour. I rekon it is a replacing question, i got something like 1/8 for each of my branches on my tree diagram. If it was something like drawing balls out of a bag or something, then non-replacement would make sense, but it was jus choosing squares, so i think it would be replacement included.

 

[mnhsc06comeonz]

i got the same as UzurOger and stYlez YIEW

fark yeh then i got
a) I) 1/8
ii)i got 1/4 and
ii) a 3/4 or something like that cant remember!!!

HOPE U BOTH ARE RIGHT!!!