Standard Math Q+A Thread

[Juliesokha]

What is the method of study for maths when I've done heaps of past papers?

Heyy, samee but guess what? there is never enough to learn! So what I do is that I'll go back and do ALL of those papers again. I do them until the point that I sometimes even remember the answers to some of the questions!! (this sounds crazy but yea)

[Potatohater]

Heyy, samee but guess what? it is never enough to learn! So what I do is that I'll go back and do ALL of those papers again. I do them until the point that I sometimes even remember the answers to some of the questions!! (this sounds crazy but yea)

I've been doing this too! It got to a point where in my final internal assesment I recognised all the questions as past paper questions except a few, and it was my best exam because of it.

[bridie_2345]

Hi there the correct answer is B, could someone please explain how to do this? Thanks! X

[RuiAce]

Hi there the correct answer is B, could someone please explain how to do this? Thanks! X

This type of question has been removed from the syllabus as of 2014. (Back in the past, they were provided the formula for the PV of an annuity. It has now been removed.)

[bridie_2345]

hey there i was wondering if anyone had any questions that focus on the year 11 content needed for the general maths hsc exam? Thanks so much!

[ca052267]

Questions like this always stuff me up.

Do I calculate the probability from the total surveyed, or the total number of males surveyed?

[katie,rinos]

Questions like this always stuff me up.

Do I calculate the probability from the total surveyed, or the total number of males surveyed?

Hey,
It's from the total surveyed as the question asks that the person is selected 'from the surveyed group' (which was the total 150 people)
Hope this helps

[RuiAce]

Questions like this always stuff me up.

Do I calculate the probability from the total surveyed, or the total number of males surveyed?

On top of what Katie said, it's really about looking out for the wording.

When the question is given without some kind of "condition", you should anticipate that you're calculating a probability against the entire sample space. (Which is, of course, the surveyed group here.)

If instead, the question read something like "Out of all the males, how many do not own a mobile phone?" then you would have the condition that you're only considering the males. That's when you would divide by 70 and not 150.

[ca052267]

Hey,
It's from the total surveyed as the question asks that the person is selected 'from the surveyed group' (which was the total 150 people)
Hope this helps

On top of what Katie said, it's really about looking out for the wording.

When the question is given without some kind of "condition", you should anticipate that you're calculating a probability against the entire sample space. (Which is, of course, the surveyed group here.)

If instead, the question read something like "Out of all the males, how many do not own a mobile phone?" then you would have the condition that you're only considering the males. That's when you would divide by 70 and not 150.

Thank you!!

I was stressing out because I usually get them right, but when I was marking, I got it wrong.

I realised afterwards that I had looked at the wrong answer... but at least you cleared it up.

[Aaron2230]

Can someone explain to me how to find the upper and lower quartile again for this question i havent done it in a while. please and thank you

[ca052267]

Can someone explain to me how to find the upper and lower quartile again for this question i havent done it in a while. please and thank you

Would the answer be 172-136 = 36?

From what I gathered you just calculate the quartile values straight form the ogive. Not sure if I'm right though..

[Aaron2230]

Would the answer be 172-136 = 36?

From what I gathered you just calculate the quartile values straight form the ogive. Not sure if I'm right though..

what i was wondering i how do i find the ogive again. the answer is correct just forgot how to do it

[Potatohater]

Do we need to know the volume of a sphere?
Only the surface area formula is on the sheet and I don't remebr learning it but it's in the 2001 past paper I'm trying to do 

[RuiAce]

what i was wondering i how do i find the ogive again. the answer is correct just forgot how to do it

The graph is the ogive.

The ogive and the cumulative frequency polygon (aka cumulative frequency graph) are the same thing.
__________________________________________

Because in total we have 400 observations (or frequencies, not sure how you prefer to call it in general), the upper quartile is when the ogive reaches a cumulative frequency of 300. Additionally, the lower quartile is when the ogive reaches a cumulative frequency of 100.

From there, you just read across. It appears as though the cumulative frequency reaches 300 when the height reaches 172, and it reaches 100 when the height reaches 136. So 172 and 136 are the upper and lower quartiles (and as already mentioned, the difference between them is the IQR).

[RuiAce]

Do we need to know the volume of a sphere?
Only the surface area formula is on the sheet and I don't remebr learning it but it's in the 2001 past paper I'm trying to do 

The syllabus changed in 2013 and in the old formula sheet they give you the formula for the volume of a sphere.

Taking a look at the updated syllabus, I do not see it in the HSC Maths General 2 section (although I did see it in the General 1 section). So I presume it has been removed.

EDIT: I checked with Steph. It still appears from time to time so it's best to know the formula just in case.