Standard Math Q+A Thread

[bridie_2345]

Hey there was just wanting to know the difference between frequency and relative frequency for probability?
Thanks heaps!

[morning_sunshine]

Hey guys

So I have a few questions for whoever is lucky enough to answer these...
1. Make x the subject of the formula y=k-mx
      Now I get how to do it but in the worked solutions insted of y-k  it's telling me it is k-y/m    ?

2. Chloe holds a provisional license. Her allowable Blood Alcohol Content (BAC) to drive is zero. She knows that the liver breaks down alcohol at an average rate of 0.75 standard drinks per hour. If she consumed 10 standard drinks from 10pm to 2am what is the earliest time that she could legally drive to work?
A. 11.20 am
B. 11.33 am
C. 3.20 pm
D. 3.33 pm
    So since there is no mass I don't know what her BAC is. Am I supposed to work out her weight first and then continue or?

3. Ari borrowed $3340 for a period of 11 months. In total he repaid $4022. The simple interst rate per annum is:
A. (4022-3340) / (3340x11) x100%
B. (3340) / (4420x11) x100%
C. {12x(4022-3340)} / (3340x11) x100%
D. (12x3340) / (4022x11) x 100%

And finally

[RuiAce]

Hey guys

So I have a few questions for whoever is lucky enough to answer these...
1. Make x the subject of the formula y=k-mx
      Now I get how to do it but in the worked solutions insted of y-k  it's telling me it is k-y/m    ?

2. Chloe holds a provisional license. Her allowable Blood Alcohol Content (BAC) to drive is zero. She knows that the liver breaks down alcohol at an average rate of 0.75 standard drinks per hour. If she consumed 10 standard drinks from 10pm to 2am what is the earliest time that she could legally drive to work?
A. 11.20 am
B. 11.33 am
C. 3.20 pm
D. 3.33 pm
    So since there is no mass I don't know what her BAC is. Am I supposed to work out her weight first and then continue or?

3. Ari borrowed $3340 for a period of 11 months. In total he repaid $4022. The simple interst rate per annum is:
A. 4022-3340/3340x11 x100%
B. 3340/4420x11 x100%
C. 12x(4022-3340)/3340x11 x100%
D. 12x3340/4022x11 x 100%

And finally

\begin{align*}y&=k-mx\\ y+mx&=k\\ mx&=k-y\\ x&=\frac{k-y}m\end{align*}
Is that screenshotted question really general math material? Like I know why the answer is B but it feels awkward trying to explain the reasoning for it because i don't know what general math students are taught.

Hey there was just wanting to know the difference between frequency and relative frequency for probability?
Thanks heaps!

Relative frequency is different in that it is the probability itself. Albeit, the experimental probability.

Suppose in 36 dice rolls the number five appeared 5 times. The frequency of five appearing was obviously just 5, but the relative frequency is 5/36.

[morning_sunshine]

\begin{align*}y&=k-mx\\ y+mx&=k\\ mx&=k-y\\ x&=\frac{k-y}m\end{align*}
Is that screenshotted question really general math material? Like I know why the answer is B but it feels awkward trying to explain the reasoning for it because i don't know what general math students are taught.Relative frequency is different in that it is the probability itself. Albeit, the experimental probability.

Suppose in 36 dice rolls the number five appeared 5 times. The frequency of five appearing was obviously just 5, but the relative frequency is 5/36.

Thanks for your help! Yes the screenshotted one is a general maths trial question but I feel like I should know how to do it in case it comes up in the HSC ya know

[yopenelope]

I was wondering, if I'm ranked 20th in General for my school (ranked 20 out of 77) - Probably around 30 people that do general maths in my school gets pretty bad marks. & I know that general scales badly.. So i was wondering is it still possible for me to get a band 6 if I got 90-100% raw mark for my final HSC exam?

[Suffering]

I don't know if this thing is still active but I've come across an issue, I've always learnt to NOT round in the middle of  a question in HSC general maths 2, however in doing past papers and going through the BOS answers for said papers I have noticed that they DO round in the middle of a question - so what am I supposed to do? I don't want to get all the answers wrong, but rounding in the middle of a question just seems wrong to me; even though BOS does it... Any help would be appreciated.

[jamonwindeyer]

I was wondering, if I'm ranked 20th in General for my school (ranked 20 out of 77) - Probably around 30 people that do general maths in my school gets pretty bad marks. & I know that general scales badly.. So i was wondering is it still possible for me to get a band 6 if I got 90-100% raw mark for my final HSC exam?

Definitely possible! This guide has the specifics but that is definitely still achievable for you

I don't know if this thing is still active but I've come across an issue, I've always learnt to NOT round in the middle of  a question in HSC general maths 2, however in doing past papers and going through the BOS answers for said papers I have noticed that they DO round in the middle of a question - so what am I supposed to do? I don't want to get all the answers wrong, but rounding in the middle of a question just seems wrong to me; even though BOS does it... Any help would be appreciated.

If you are concerned, don't round until the end! That is definitely considered correct even in the sample solutions do round earlier

[RuiAce]

Thanks for your help! Yes the screenshotted one is a general maths trial question but I feel like I should know how to do it in case it comes up in the HSC ya know

Well, I'm not sure how I can effectively convince a general student about it, but...

[RuiAce]

3. Ari borrowed $3340 for a period of 11 months. In total he repaid $4022. The simple interst rate per annum is:
A. 4022-3340/3340x11 x100%
B. 3340/4420x11 x100%
C. 12x(4022-3340)/3340x11 x100%
D. 12x3340/4022x11 x 100%

Can you please put some more brackets to emphasise what's going on with the fractions? A could easily be interpreted as \( 4022 - \frac{3340}{3340}\times 11 \times 100\text{percent} \)  even though you probably didn't mean it like that.

[morning_sunshine]

Ok thanks so much Rui means a lot

Could you help me with the other 2 that were mentioned also which I edited and placed below?

Thanks in advance

2. Chloe holds a provisional license. Her allowable Blood Alcohol Content (BAC) to drive is zero. She knows that the liver breaks down alcohol at an average rate of 0.75 standard drinks per hour. If she consumed 10 standard drinks from 10pm to 2am what is the earliest time that she could legally drive to work?
A. 11.20 am
B. 11.33 am
C. 3.20 pm
D. 3.33 pm
    So since there is no mass I don't know what her BAC is. Am I supposed to work out her weight first and then continue or?

3. Ari borrowed $3340 for a period of 11 months. In total he repaid $4022. The simple interst rate per annum is:
A. (4022-3340) / (3340x11) x100%
B. (3340) / (4420x11) x100%
C. {12x(4022-3340)} / (3340x11) x100%
D. (12x3340) / (4022x11) x 100%

[kaseyv]

How to find the correlation coefficient r?? Are we meant to know a formula for that or will it not be in the HSC exam? I was doing a Sydney Grammar Trial paper and it asked to find the correlation coefficient...

[RuiAce]

3. Ari borrowed $3340 for a period of 11 months. In total he repaid $4022. The simple interst rate per annum is:
A. (4022-3340) / (3340x11) x100%
B. (3340) / (4420x11) x100%
C. {12x(4022-3340)} / (3340x11) x100%
D. (12x3340) / (4022x11) x 100%

So A.

(I'm leaving that other question for the time being because I'm not quite sure how to do it either, having not done general. Someone else might get to it before I get back to it.)

[RuiAce]

How to find the correlation coefficient r?? Are we meant to know a formula for that or will it not be in the HSC exam? I was doing a Sydney Grammar Trial paper and it asked to find the correlation coefficient...

According to the formula sheet, you can work backwards using the least squares line of best fit.

If it does not work, please post the actual question.

[studyharddd]

Just wondering how to know when to use either the simple interest formula or compound interest formula and whats the difference? Unsure when to use which in some questions.

[RuiAce]

Just wondering how to know when to use either the simple interest formula or compound interest formula and whats the difference? Unsure when to use which in some questions.

I'm pretty sure they will state/hint when to use which. Please provide examples on where the confusion lies.
________________________

The main difference between simple interest and compound interest is generally overlooked. The difference lies in how the compounding actually happens.

In simple interest, we have a principal amount \( P \), and we only ever compound on top of it. This means that after one period, our interest calculated will be with respect to \( P\). After two periods, the amount will still be calculated with respect to \(P\).

In compound interest, we start with a principal amount \( P\), but we only ever compound on top of that one ONCE. Instead, after we compound it once, we then compound on the NEW amount. So whereas after one period we compound on top of \( P \), for the second period we compound on top of \( P \times \text{the interest factor} \) instead.

And well, the interest factor (a.k.a. compounding factor) is just a fancy name for \( 1+r \).