VCE General & Further Maths Question Thread!

[Yacoubb]

how do you do Q4 of core for VCAA 2008 EXAM1
http://www.vcaa.vic.edu.au/Documents/exams/mathematics/2008furmath1-w.pdf

i got D. because the IQR = 90-20= 70 and the median = 35. thus median is half of the IQR.

Yeah I got D as well; never quite understood why it couldn't have been a right answer..

[soNasty]

hello can someone please help me with either of these questions on the 2011 neap trial exam thats posted online?
here's the link http://www.neap.com.au/pdf/errata/errataTEFMU34Ex1_QA_2011.pdf
question 4 and 5 in number patterns.
cheers!

[KevinooBz]

Yeah I got D as well; never quite understood why it couldn't have been a right answer..

I'll demonstrate why that is wrong through an example. Take the numbers 1, 3, 4, 5, 7, 8, 10. Median is 5, Q1 is 3 and Q3 is 8. IQR=5 => IQR/2=2.5
2.5=/=5
Median=/=IQR/2
Furthermore, the median isn't the average of Q1 and Q3 e.g. in this case that would be 5.5 which clearly isn't the median. The median is the 50%ile value, but that does not necessarily mean that it's half the IQR or the average of Q1 and Q3. You can also look at skewed boxplots if you want to visualise this.

[Yacoubb]

I'll demonstrate why that is wrong through an example. Take the numbers 1, 3, 4, 5, 7, 8, 10. Median is 5, Q1 is 3 and Q3 is 8. IQR=5 => IQR/2=2.5
2.5=/=5
Median=/=IQR/2
Furthermore, the median isn't the average of Q1 and Q3 e.g. in this case that would be 5.5 which clearly isn't the median. The median is the 50%ile value, but that does not necessarily mean that it's half the IQR or the average of Q1 and Q3. You can also look at skewed boxplots if you want to visualise this.

Yeah I was thinking on the lines of skewing and how this affected it. I think because it's positively skewed, A would be a more appropriate answer.

[Zealous]

Yeah I got D as well; never quite understood why it couldn't have been a right answer..

The mean is affected by extreme values and therefore will be much higher than the median in this situation. There are 7 outliers which will all push the mean up, while the median would stay lower.

I guess D is feasible, but they want something conclusive. I don't think from a box plot we can conclude that it is exactly half of the interquartile range, it could be every so slightly off (35.5 seconds) and therefore D would be false. The scale makes it hard to see the specific times and also, time is a continous variable: the questions use "closest to" as it's impossible for us to determine an exact value, therefore we can find what's looks close to the IQR but it may not actually be.

[Yacoubb]

The mean is affected by extreme values and therefore will be much higher than the median in this situation. There are 7 outliers which will all push the mean up, while the median would stay lower.

I guess D is feasible, but they want something conclusive. I don't think from a box plot we can conclude that it is exactly half of the interquartile range, it could be every so slightly off (35.5 seconds) and therefore D would be false. The scale makes it hard to see the specific times and also, time is a continous variable: the questions use "closest to" as it's impossible for us to determine an exact value, therefore we can find what's looks close to the IQR but it may not actually be.

Yeah, fair enough. I guess going with the most conclusive answer all the time should do the trick.

[lala1911]

Hi.
When both the cosine and sine rule are applicable, which rule should be favoured?
I was doing the vcaa 2012 exam 2 section for Geo/Trig, question 4d and the assessors report included the sine rule and got the answer 43.118 although the cosine rule can still be applied. Does it matter which one is used?
REPORT: http://www.vcaa.vic.edu.au/Documents/exams/mathematics/2012/fm2_assessrep12.pdf
EXAM: http://www.vcaa.vic.edu.au/Documents/exams/mathematics/2012/2012furmath2-w.pdf

[abcdqdxD]

It appears that the question required the application of BOTH the sin rule and cos rule..

[lala1911]

It appears that the question required the application of BOTH the sin rule and cos rule..

Yeah. True. I didn't explain it properly, I mean the second part of the question to get the angle.

[abcdqdxD]

I think you will still get the marks if your working out is correct

[tcstudent]

FOR THE CORE

Question states: IF the deaseasonalised number of ice creams sold in summer is 431, then the actual summer sales is closet to? the seasonal index for summer is 1.34

i got for this answer 578, answer is 532, why?
322
431
446
532
578

[BLACKCATT]

I dont see how it can be 532

[abcdqdxD]

578 is correct unless you got the seasonal index wrong

[aestheticatar]

'Show that'

What's the difference between 'showing' in comparison to just calculating the answer as per usual with working out? How in depth do we have to 'show' how we received our answer?

Fankz guyz 

[lala1911]

The working out that led you to getting the answer.