Solutions (3 Viewers)

[LostAuzzie]

What was the answer for 5) d) iii)?

I got (100\300) * (100\299) * (100\298)

However I suck at probability, is this correct though?

I did (300/300) * (200/299) * (100/298)

 

[phil2005]

but the question stated 'interest is calculated on the balance at the beginning of the year' and since n=12.2325

therefore on the 13th year the final payment will be made...

therefore
2005 + 13 = 2018
therefore the coucil makes the final payment in 2018

Ahhh very good point...... i've been thinking all along it said at the END of each year. I concede then - it is 2018 .

 

[lourai*87]

bugger!!! I mutiplied by 3 for d) iii BUGGER!!

I was so thinking i got a good many questions out only to realise i screwed ip - for example Q7..stupit stupid mistake. Anne's was an arithmatic series, Kay's was geometric. I did both arithmatic. *kicks self (repeatedly)*

 

[Oso]

Yeah i agree with you that dV/dt = -80L/s DOES imply that it's leaving, however when putting it into a sentence I like "draining at 80L/s" because to me that makes more sense - the draining implies the negative nature of the rate.

As for 5c, here's the solution:

y = 2e^x + 3x
dy/dx = 2e^x + 3

Since gradient of y = 5x – 3 is 5 and it is gradient is parallel to this line:

2e^x + 3 = 5
2e^x = 2
e^x =1
Therefore x = 0

When x = 0, y = 2x1 + 0 = 2

Therefore P is (0,2)

Thanks mate, I see I went wrong when finding the derivitive, but I may have scraped the other two marks...

 

[Tom-Tom]

Geez... should have read the question... I just said in the 12th year!

i did the same thing!! i think we wud get 1 mark 4 dat.

 

[starbaaa]

i did the same thing!! i think we wud get 1 mark 4 dat.

I did almost the same thing, except i wrote in the 13th year. I'm kicking myself -- when I read the question I said to myself, "right, the'yre asking for a specific year. remember to write the actual year". and did i? no. I just wrote "final repayment in the 13th year". I'm positive that all my working was correct, so I'm hoping for a mark.

 

[Jago]

I did (300/300) * (200/299) * (100/298)

yeah i think i did that too.

 

[cheese66]

qn 10

wat did u guys get 4 qn 10 b (iii)?

was it root 2?

 

[Famine]

Very close mate -
P(One of each) = (100/300) * (100/299) * (100/298) * 6

You have to multiply by six because there are six possible arrangments:

i.e.
Red, Green, Blue
Red, Blue, Green
Green,Blue,Red
Green,Red,Blue
Blue,Green,Red
Blue,Red,Green

You'd probably get 1 out of 2 for what you wrote though !

Doh! Seems so obvious now. Oh well, what can you do.

 

[fullmetaljacket]

I feel like I got about 15%.

 

[[Damo]]

Ahhh very good point...... i've been thinking all along it said at the END of each year. I concede then - it is 2018 .

I put 2018 too. coz n=12.23
how could it be 2017!?

 

[[Damo]]

Crap!! Yeah, I'm pretty sure that's right... I just screwed myself by not thinking and putting 1/300 * 1/299 * 1/298 Dammit!!

Im in the same boat m8!!

 

[princessj]

i got 2017 too

 

[klaw]

I put after 13 yrs

 

[Bookie]

I put 12.whateverm, then wrote "during the 13th year"

 

[Bookie]

By the way, for 10) b) iii) I put 17 m 34 s, but I think we were to put it as a fraction of 1 [ie 0.29]. Hopefully get a mark for it though. I tried hard for that question.

And one other (6biii i think) when does the rate of water flow the quickest. I put at the 60th minute, but it shouldve been the 1st minute.

Other than that, i'm sweet

 

[mmmegan]

aahh - i got t=3

 

[rnitya_25]

i got 2017 too

yah me too, and i think that is correct, because i was doing a past paper and they had this kinda question, and at the end, they added it to the initial year to find out which year it was. which it why i addedd it to 2005 and got during the year 2017.

 

[jennylim]

I know this sounds rather stupid, but i find the easiest way is to count it out with your fingers.

A1 = End of 2005
A2 = End of 2006
A3 = End of 2007
A4 = End of 2008
A5 = End of 2009
A6 = End of 2010
A7 = End of 2011
A8 = End of 2012
A9 = End of 2013
A10 = End of 2014
A11 = End of 2015
A12 = End of 2016

Thus, since n was slightly greater than 12,
It follows that it would be repaid in 2017

I think that it would make more sense if it said "equal annual repayments of $480000 until An < $480000 when the remaining balance will be paid in full". Either that or everyone has screwed up the question completely!

What's done is done i guess...

I did the same thing in the exam - wrote down each year and the payment beside it. I got end of 2017...hope it's ok.

Additionally with Q10b...

I got 7/16 for the first bit, and 17 minutes 34 seconds for the second. Because there would be two triangles, right, making up a square with area (1-t)^2? And then you just solve the quadratic with (1-t)^2 = 1/2....

At least, that's what I did. I'm pretty sure it's right, because it makes sense (if 15 minutes is 7/16 which is pretty close to half, then 17 and a half minutes could reasonably be 1/2). But we'll see.

 

[r.haidar]

this thread should be closed... each post makes more and more confident that i fucked up lol not really but im sure someone out there believes it! let it go people, just wait for ur hsc results lol so impatient...

peace out
ralph