Mathematics: Post your doubts here!

[PhyZac]

Mate look: if you have two classes such as 10-19 and 20-29, then their class boundaries should be 9.5-19.5 and 19.5-29.5. That's what I was taught. I think you would concur.

Yea I know, I got your point

But, we cant have -ve number in some cases (many cases) so consider 0!

 

[Scafalon40]

Yea I know, I got your point

But, we cant have -ve number in some cases (many cases) so consider 0!

So you support Dug's theory that class boundaries aren't required when calculating midpoints? I am considering 0. It's driving me mental!

 

[PhyZac]

So you support Dug's theory that class boundaries aren't required when calculating midpoints? I am considering 0. It's driving me mental!

Nope, I don't support that, I agree to your point in that case.

But I think this will satisfy you
http://www.examsolutions.net/maths-revision/statistics/representing-data/histograms/tutorial-1.php

 

[daredevil]

For 0 it stays zero, keep it like a rule.!!

Yeah I know, and that's what confuses me the most!

u know about these class boundaries and stuff our sir told us that we can either subtract and add respectively to the 1st and the second value or we cud just add 1 to the second one or subtract one from the first one... just have to make a difference with 1. and given this question i dont think there's much we can do about the negative value so its better to add 1 to the second one.

btw the answers to these class widths are ambigous because they are different in almost every marking scheme. just make ur best judgement according to the question is pretty much all u can do.
also if u take 10.5 till 20.5 in this specific example under discussion u will still get a decimal value for the mean (15.5) ryt?

 

[Scafalon40]

Nope, I don't support that, I agree to your point in that case.

But I think this will satisfy you
http://www.examsolutions.net/maths-revision/statistics/representing-data/histograms/tutorial-1.php

Youtube doesn't work here mate
I have all these examsolutions videos downloaded, though. It's gonna take me some time to find it. Hold on!

 

[Scafalon40]

u know about these class boundaries and stuff our sir told us that we can either subtract and add respectively to the 1st and the second value or we cud just add 1 to the second one or subtract one from the first one... just have to make a difference with 1. and given this question i dont think there's much we can do about the negative value so its better to add 1 to the second one.

btw the answers to these class widths are ambigous because they are different in almost every marking scheme. just make ur best judgement according to the question is pretty much all u can do.
also if u take 10.5 till 20.5 in this specific example under discussion u will still get a decimal value for the mean (15.5) ryt?

Not 10.5, 9.5!
And you're right about these different markschemes. I guess there's nothing we can do....
Btw if you could just provide me with some sort of link, some reference etc I'd be quite satisfied
Thanks anyway

 

[Scafalon40]

Nope, I don't support that, I agree to your point in that case.

But I think this will satisfy you
http://www.examsolutions.net/maths-revision/statistics/representing-data/histograms/tutorial-1.php

I've watched the video. It still doesn't make sense. If you take the class boundaries as 0 and 9.5, you'll get the midpoint as 4.75, whereas the mark scheme clearly states it as 4.5. That's what I don't understand!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Scafalon40]

I found this.http://ncalculators.com/math-worksheets/how-to-calculate-class-interval-arithmetic-mean.htm
errrrrrr........

 

[sma786]

daredevil ,i have a doubt
http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s09_qp_6.pdf , in the markscheme (http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s09_qp_6.pdf) where did they get 0.674 for question 1?

 

[daredevil]

daredevil ,i have a doubt
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s09_qp_6.pdf , in the markscheme (http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s09_qp_6.pdf) where did they get 0.674 for question 1?

ok i'm pretty sure i did this question for my mocks prep but i am totall null blank ryt now :O if anyone answers then tag me too .... it just isnt hitting me -_-

 

[daredevil]

I found this.http://ncalculators.com/math-worksheets/how-to-calculate-class-interval-arithmetic-mean.htm
errrrrrr........

so they havent made class boudaries here?! :O

 

[sma786]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s09_qp_6.pdf
Question 3, (ii), (73.5-80/5.36) -> answer is -1.211 who's Φ is 0.8871
in the markscheme they say, 1-Φ(answer), which would be 1-0.8871 = 0.1129, but the answer in markscheme is 0.8871, why?!

( daredevil)

 

[Esme]

I see a lot of stats related posts here, anyone up for answering P3 doubts ?

 

[Esme]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_32.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_ms_32.pdf

Q9 ii) I can't seem to get the answer, even though I think I'm integrating it right.
We have to integrate x lnx^2
I'm doing it by integration by parts but I don't get the answer as in the marking scheme..
Anyone? Please show me the workings

applepie1996

 

[Esme]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_qp_32.pdf
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_ms_32.pdf

Q7 iii) why is arg(1+2i) - arg(1-3i) = arg(u) ??

Anika Raisa ?

 

[Sanis]

any urgent helpers? :O

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w11_qp_33.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_ms_33.pdf

I need help in q1, q6ii), q10i) Thanks in advance

 

[sma786]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s06_qp_6.pdf

Question 6, i and ii, how to get the answer?

 

[Dug]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_32.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_ms_32.pdf

Q9 ii) I can't seem to get the answer, even though I think I'm integrating it right.
We have to integrate x lnx^2
I'm doing it by integration by parts but I don't get the answer as in the marking scheme..
Anyone? Please show me the workings

applepie1996

ln(x²) is not the same as [ln(x)]². Try again using the latter!

 

[Dug]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s06_qp_6.pdf

Question 6, i and ii, how to get the answer?

i)
First round: 32 teams, 16 winners, 16 losers
These 16 losers play only one game as they are knocked out in the first round.

ii)
Second round: 16 teams, 8 winners, 8 losers
The 8 losers in this round play exactly two games. They qualify for the second round after winning in the first but then get defeated!

 

[sma786]

i)
First round: 32 teams, 16 winners, 16 losers
These 16 losers play only one game as they are knocked out in the first round.

ii)
Second round: 16 teams, 8 winners, 8 losers
The 8 losers in this round play exactly two games. They qualify for the second round after winning in the first but then get defeated!

thnksss!