Solutions (2 Viewers)

[littlebinzy]

Well so far I've noticed a few marks that I've lost... so maybe I won't be over 100 after all

 

[Chiro]

Probability

ummm guys... it cant be 100/300 * 100/299 * 100/298 * 6

although most of that is correct, i take it that u have decreased from 300 to 298 as each ticket drawn is not replaced... well the point of saying that, is that 100 is not going to be how many tickets are left for the second and third draw... uve taken one out already, remember?

so really, its: 100/300 * 99/299 * 98/298 * 6

does that make sense? the BOS was very clever, if u look back, there is a question mirror image to the working out needed to answer that question, just based on a different scenario.. many people that year didnt decrease the numerator as well as the denominator, and thus lost most of the marks... too bad they got people again

 

[rachey_poo]

but aren't there still 100 of the other colours left???
so really couldnt your first choice be a probability of 1, and then 100/299 and 100/298 * 6? this is not what i did...i only times by 3...stupid head stupid head...??? im so lost

 

[MichaelPH]

No, it asks for the 3 different colours, so once green is drawn, there are only 99 green tickets left, but there is still 100 blue and 100 red. Because it asked for the probability of getting 3 different colours it has to be 100/300*100/299*100/298*6 because each colour is only getting drawn once.

 

[rachey_poo]

agreed....i think

 

[MichaelPH]

Over all, but, I think i got 73 raw score, which i'm not so happy about, but I found a lot of the little things difficult. Its funny, i don't mind differentiation or calculus, but i can't stand the stuff pple find easy, like coordinate geometry. How the hell did people find point D in Q3???

 

[rachey_poo]

if you proved part (i), all you had to do was find the equation on the line OC and then solve lines AD and OC simultaneously to find D!...i think.....

 

[jennylim]

No, it asks for the 3 different colours, so once green is drawn, there are only 99 green tickets left, but there is still 100 blue and 100 red. Because it asked for the probability of getting 3 different colours it has to be 100/300*100/299*100/298*6 because each colour is only getting drawn once.

It better be, because that's what I did. I actually drew a frigging tree diagram for this question and confused myself like crazy, before resorting to a bit of 3u maths - ie, (3P3)*100/300*100/299*100/298.

The only one that really stumped me badly was that stupid one about the maximum rate it was being emptied...that's t=0, right? Because I differentiated it and found the st pt only to realise it was a minima not a maxima. Grr.

 

[LordSeafood]

Well i believe i got about 40%

I finished all i could do after 2hr 15mins

 

[Srixon]

man for that question 3 how to find the points i just guessed them
to be like D(8,4) and E (11,4) but i think i might of changed them to D(7,4) E(10,4)

 

[Jago]

It better be, because that's what I did. I actually drew a frigging tree diagram for this question and confused myself like crazy, before resorting to a bit of 3u maths - ie, (3P3)*100/300*100/299*100/298.

P(3 different colours) = 1 x 200/299 x 100/298

1: because it doesnt matter what colour the 1st one is

200/299: because having chosen the first one being of x colour, there is 200 non-x-coloured tickets left.

100/298: same as above, sort of. there's only 1 colour that hasn't been picked, and theres 100 of those tickets.

 

[motlai]

I've never been too flash at maths, but heres how I did that probability of three diff colours question:

It doesn't matter what the first colour, so its prob is 300/300

For the second draw, there are two colours that aren't the same as the first, so its prob is 200/299

For the third, there's now one colour that has not been drawn, so its prob is 100/298

And so P(E) is whatever those three multiplied equals

 

[motlai]

woah...Jago and i posted teh same thing at the same time!

 

[Jago]

Over all, but, I think i got 73 raw score, which i'm not so happy about, but I found a lot of the little things difficult. Its funny, i don't mind differentiation or calculus, but i can't stand the stuff pple find easy, like coordinate geometry. How the hell did people find point D in Q3???

D was on the line OC but has the gradient of BC

Edit: haha goodwork, i had to explain this type of question (probability) to some friends just before our trial so im pretty sure i'm right on this.

 

[jennylim]

P(3 different colours) = 1 x 200/299 x 100/298

1: because it doesnt matter what colour the 1st one is

200/299: because having chosen the first one being of x colour, there is 200 non-x-coloured tickets left.

100/298: same as above, sort of. there's only 1 colour that hasn't been picked, and theres 100 of those tickets.

great!! we got the same thing (0.224461852). so that's brilliant.

 

[veterandoggy]

if you still need to pay a little bit, then you havent paid it off, have you?

it's 2018. it is hard, questions like thes need too much experience with past questions, since the answer can be taken both ways

 

[tabularasa]

These are good they are making me feel better about my work. From my calucaltions i passed so thats good.

 

[sam_account]

man i feel so dumb!!!!! coz i didnt draw graph to scale , i stuffed up question 10 (b) (ii) and consequently (iii)...!!!!!!argh!!!!

would they give a mark for "recognising to find the area between the ineqaulities for part (i)".. and "recognising that area needs to be .5 for part (iii)"

hopefully still get 3/5 for 10 (b)...

also did prob. question wrong!!!!!farout!!!!!!

so probably only end up with 115 or 116/120!!!!!!!!

would 115/116 be enough for a 98% scaled?

ty...

 

[jebba_d]

That's what I got, t=0.

I find it hard to comprehend, though that the water is draining the fastest before any time has passed

mmmm well it makes sense. if u think of it from a physics pooint of view....the tanks full at the start, so at t=0 there is the most pressure pushing down, as the tank empoties the pressure drops and the rate of change is smaller too

 

[Cloak]

Wouldn't it be smarter for someone to do all the questions and post them in perhaps a jpeg scan. I barely past so no point me doing anything.