VCE Methods Question Thread!

[rozmaaate]

Hey guys I’m stuck on question 2d  some help would be greatly appreciated , (cas required)

Edit: the equation should read d= 1.8cos(𝛑t/6)+ 3

[Umar but with O]

Hi, I was wondering which topics from Methods 1/2 are relevant to Units 3/4
(i.e., required in order to understand the material in Units 3/4).

I am currently using Jacaranda brand books (I've heard some -ve reviews for this brand) for maths so any suggestions as to which brand books to take for maths will also be greatly appreciated.

Thanks

[SS1314]

Hi, I was wondering which topics from Methods 1/2 are relevant to Units 3/4
(i.e., required in order to understand the material in Units 3/4).

I am currently using Jacaranda brand books (I've heard some -ve reviews for this brand) for maths so any suggestions as to which brand books to take for maths will also be greatly appreciated.

Thanks

Cambridge is the best because of the hard questions.

In terms of relevant topics I would say all the topics are relevant to some extent. The most important/relevant topics are functions/transformations, calculus, basic probability and binomial distribution. The least relevant topic is probably counting methods, however you should still have an understanding of combinations since it is part of the binomial distribution formula.

[keltingmeith]

Hey guys I’m stuck on question 2d  some help would be greatly appreciated , (cas required)

Edit: the equation should read d= 1.8cos(𝛑t/6)+ 3

So I drew a Desmos graph to hopefully make things clearer for you. You have a pole that's 6m high - this pole is the purple line. I've drawn is every time x (or t) is a multiple of 3 to give you an idea of how much the pole is covered by water. Remember that at each point, the cosine graph represents what level the tide is at. So for example, at x=3, you can see that the cosine graph and the pole intersect at approximately y=3. This means that the pole is 3m under the water. Then, at x=6, it looks like the curve intersects the pole at y=1.2, and so the pole is 1.2m under the water. But that's not what the question is asking - it wants to know when the pole is 4m OUT of the water. Well, at x=3, if the pole is 3m under the water, then it is 6 (its height) - 3 =3 metres out of the water. And at x=6, the pole is 6-1.2=4.8 metres out of the water. Using this information, do you think you can figure out what equation to use when you want the pole to be at least 4 metres out of the water?

[rozmaaate]

So I drew a Desmos graph to hopefully make things clearer for you. You have a pole that's 6m high - this pole is the purple line. I've drawn is every time x (or t) is a multiple of 3 to give you an idea of how much the pole is covered by water. Remember that at each point, the cosine graph represents what level the tide is at. So for example, at x=3, you can see that the cosine graph and the pole intersect at approximately y=3. This means that the pole is 3m under the water. Then, at x=6, it looks like the curve intersects the pole at y=1.2, and so the pole is 1.2m under the water. But that's not what the question is asking - it wants to know when the pole is 4m OUT of the water. Well, at x=3, if the pole is 3m under the water, then it is 6 (its height) - 3 =3 metres out of the water. And at x=6, the pole is 6-1.2=4.8 metres out of the water. Using this information, do you think you can figure out what equation to use when you want the pole to be at least 4 metres out of the water?

Hey mate I think I got the solution to the question however the original wording of the question threw me off me off with saying “depth” of the water instead of the tide level , as depth is generally a distance below a point eg: sea level . That being said here’s my working to the question . I think I am correct

[FlammaZ]

The amount of a certain chemical in a type A cell is normally distributed with a mean of 10 and a standard deviation of 1. The amount in a type B cell is normally distributed with a mean of 14 and a standard deviation of 2. To determine whether a cell is type A or type B, the amount of chemical in the cell is measured. The cell is classified as type A if the amount is less than a specified value c, and as type B otherwise.
a-If c=12, calculate the probability that a type A cell will be misclassified, and the probability that a type B cell will be misclassified.
b-Find the value of c for which the two probabilities of misclassification are equal.

[james.358]

Hey FlammaZ!

This is an interesting question. The difficulty does not lie in solving it, but instead understanding what it is asking for.

Firstly, lets define the distributions

A ~ N (10, 1), and B ~ N (14, 2²)

Question a)

For Chemical A to be misclassified, if the amount has to be more than c, which is 12. Conversely for Chemical B.

Now that we have interpreted this, the question becomes relatively straightforward.

The probability for A to be misclassified is Pr (A > 12) = 0.02275
The probability for B to be misclassfied is Pr (B < 12) = 0.1587

Question b)

For the probability of misclassification to be equal, Pr (A > c) = Pr (B < c)
You can solve this on the CAS for c to find c = 34/3

Hope this helps!
James

[TheEagle]

Hey guys

Is finding the sample size in the course for 2020?

[keltingmeith]

Hey guys

Is finding the sample size in the course for 2020?

I mean, yes, but also no? Sample size is an incredibly broad term that's in every single chapter of probability and statistics, so in some cases it's gone, in others it's very much still there. You'll have to be a bit more specific

[TheEagle]

I mean, yes, but also no? Sample size is an incredibly broad term that's in every single chapter of probability and statistics, so in some cases it's gone, in others it's very much still there. You'll have to be a bit more specific

True. I'm specifically referring to chapter 14C from the Cambridge textbook. It's pretty much all CAS work but my friend is saying it has been removed from the course for this year.

[p0kem0n21]

how would i convert an equation from slope-intercept form (y=mx+c) to standard form (ax+by=c) using ONLY cas (tinspire specifically)? i know it's often easier to do this by-hand but....just in case

[keltingmeith]

True. I'm specifically referring to chapter 14C from the Cambridge textbook. It's pretty much all CAS work but my friend is saying it has been removed from the course for this year.

In this case - there's nothing that has been removed from the study design relating to the binomial distribution. So technically, no, it hasn't been removed. I'm going to be honest, I don't remember having seen these types of questions being asked for a while (although S_R_K is probably a better judge of that than me), so if you're that worried, feel free to take the gamble. However, they're also not that hard, it's just different thinking - so could be worth learning that section so you get the new way of thinking.

how would i convert an equation from slope-intercept form (y=mx+c) to standard form (ax+by=c) using ONLY cas (tinspire specifically)? i know it's often easier to do this by-hand but....just in case

I don't know of a CAS function that can do this, but I cannot think of a single instance you'll be required to do this on a CAS and not in your head or on the page. All you do is multiply both sides by the denominator of m, then by the denominator of c, then move the x term to the other side. TBH, if the question asked (and I can promise you - VCAA will never ask this) you, "Convert y=(5/6)x + (2/3) into standard form using only your CAS", you should be able to do that in your head and just write, "by CAS, 18y-15x = 12". It's not like you submit your calculator for inspection after the exam, so.

Perchance there's a situation you imagined in your head you might need it for, and I might be able to help assuage those fears?

[p0kem0n21]

haha nah im not scared, it's just that we have a ti-nspire assignment (im in year 10) and one of the things asked of us to do is to convert slope-intercept to standard form but...... i guess i can pretend i used cas xD

[TheEagle]

Anyone know if continuous random variables are still in the course or not (i.e ch 15 of Cambridge)?

[The Cat In The Hat]

What's in the 2020 probability curriculum: 13AB, Ch 14, Ch 16, understanding of the importance of shape (positive and negative skew & symmetry), centre (mean = µ = average = long term expected value), spread (std dev = √var = sigma)

So, no.