Mathematics: Post your doubts here!

[uzamaki]

3. The random variable X is normally distributed with mean µ and variance 21.0. Given that P(X > 10.0) = 0.7389,(w06_6) find the value of µ.please help me out with this problem anyone! aren't we supposed to use (X-mean)/sd but the answer came wrong!

 

[musiclover gurl]

You should use the marking scheme for answers. Youshould then post what you did not understand from it then I can explain

Well then, I cant even do the first part! Help?

 

[Shujaat Khan]

Well then, I cant even do the first part! Help?

It's hard to copy paste pheta everytime, I'm using pheta=@ ok?
sin (2@+@)= sin2@cos@+ cos2@sin@ -------1
This you get in formula sheet.

Then what is sin2@ and cos2@?
sin 2@= 2sin@cos@
cos 2@= 1-2sin^2 @

Replace in first equation
2sin@cos@cos@ +(1-2sin^2 @)sin@
2sin@cos^2 @+(1-2sin^2 @)sin@
----------->cos^2 @= 1-sin^2 @
2sin@(1-sin^2 @)+ (1-2sin^2 @) sin@
2sin@-2sin^3 @+ sin@ -2sin^3 @
=3sin@ -4sin^3 @
Easy? It's all in the formula sheet you are given, you just have to substitute.

For part 2, Relatively easy you just replace x by what is given and simplify.

For part 3, solve sin 3@= 3/4
you get valueS of @ and replace in x= 2sin@/3^0.5

 

[musiclover gurl]

It's hard to copy paste pheta everytime, I'm using pheta=@ ok?
sin (2@+@)= sin2@cos@+ cos2@sin@ -------1
This you get in formula sheet.

Then what is sin2@ and cos2@?
sin 2@= 2sin@cos@
cos 2@= 1-2sin^2 @

Replace in first equation
2sin@cos@cos@ +(1-2sin^2 @)sin@
2sin@cos^2 @+(1-2sin^2 @)sin@
----------->cos^2 @= 1-sin^2 @
2sin@(1-sin^2 @)+ (1-2sin^2 @) sin@
2sin@-2sin^3 @+ sin@ -2sin^3 @
=3sin@ -4sin^3 @
Easy? It's all in the formula sheet you are given, you just have to substitute.

For part 2, Relatively easy you just replace x by what is given and simplify.

For part 3, solve sin 3@= 3/4
you get valueS of @ and replace in x= 2sin@/3^0.5

Hi...thanks I got everything right except the last part...when we solve 3@, we are supposed 6 answers but according to the marking scheme, only 3 answers are accepted. Why so? Or, is it because some of the answers are the same? Plz, can you see the question again?

 

[AreebaKausar]

I have done m entire O n A level Privately... I got A* in O level, I expect something similar in A level. I know every topic, every question, i am all set..


If there wasn't this one thing,

I absolutely absolutely fail to do PERMUTATION AND COMBINATION.. I have watched tutorials, read book..
I just don't know how to handle which question.. where to put what method,

IT SUCKS

 

[The Sarcastic Retard]

3. The random variable X is normally distributed with mean µ and variance 21.0. Given that P(X > 10.0) = 0.7389,(w06_6) find the value of µ.please help me out with this problem anyone! aren't we supposed to use (X-mean)/sd but the answer came wrong!

 

[musiclover gurl]

Hi...In the question below, I am supposed to use similar triangles in order to do the first part. Now thats the problem! I didnt know I have to use this concept for this question until I looked in the marking scheme. Now, suppose I dont have the marking scheme, how will I know this? Any idea?

Btw it is Nov 2013 P 12

 

[shazmina]

Assalamu alaikum ...
Can any one please explain me Question 10 Part (iii) of this paper ....
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s14_qp_32.pdf
Thanks in Advance

 

[The Sarcastic Retard]

Hi...In the question below, I am supposed to use similar triangles in order to do the first part. Now thats the problem! I didnt know I have to use this concept for this question until I looked in the marking scheme. Now, suppose I dont have the marking scheme, how will I know this? Any idea?
View attachment 57165
Btw it is Nov 2013 P 12

Eqn of Line : y = -3/4x + 12
Area = x * y = 12x - 3/4*x^2

 

[Rectified Spirit]

Can anyone pls help me with no. 9 (b), I cannot find out how to integrate it......9709/31/M/J/11

 

[nehaoscar]

Anyone have any revision notes for P2, P3 and S1??? like formulae, when to use, where to use, identities etc....? Thanks in advance!

 

[nehaoscar]

I have given 9709 P1 (12) for AS level last year.
I am giving A levels in 2016 summer and I am doing P3 (32) for maths
For P3 do I need to know P1 and P2 as well?

 

[The Sarcastic Retard]

I have given 9709 P1 (12) for AS level last year.
I am giving A levels in 2016 summer and I am doing P3 (32) for maths
For P3 do I need to know P1 and P2 as well?

Yeah.

 

[cristiano]

3
A sample of 36 data values, x , gave Σ(x −45) = −148 and Σ(x −45)2=3089.
(i) Find the mean and standard deviation of the 36 values. [3]
(ii) One extra data value of 29 was added to the sample. Find the standard deviation of all 37 values.[4]
No need to solve (i) solve (ii) only.
this is a past paper question. please help!!!
if you find it diificult to solve just explain the procedure.

 

[The Sarcastic Retard]

3
A sample of 36 data values, x , gave Σ(x −45) = −148 and Σ(x −45)2=3089.
(i) Find the mean and standard deviation of the 36 values. [3]
(ii) One extra data value of 29 was added to the sample. Find the standard deviation of all 37 values.[4]
No need to solve (i) solve (ii) only.
this is a past paper question. please help!!!
if you find it diificult to solve just explain the procedure.

-45+29 = -16
E(x - 45) = -148 - 16 = -164
E(x - 45)^2 = 3089 + 16^2 = 3345
Now u can solve it

 

[lemonrsiow]

A die is biased. The mean and variance of a random sample of 70 scores on this die are found to be
3.61 and 2.70 respectively. Calculate a 95% confidence interval for the population mean score.

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s14_qp_71.pdf
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s14_ms_71.pdf

How do you standardise? (σ^2)

My working:

s^2= 1/(n-1) * σ^2
2.7 = 1/(69) * σ^2
σ^2 = 2.7*69

CI = 3.61 +or- 1.96 sqrt(σ^2 / n)
=3.61 +or- 1.96 sqrt(2.7*69 / 70)

But answer is completely wrong?

 

[manya]

Assalamu alaikum ...
Can any one please explain me Question 10 Part (iii) of this paper ....
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s14_qp_32.pdf
Thanks in Advance

 

[Reus11]

In a group of 30 teenagers, 13 of the 18 males watch "K&K" on TV and 3 of th 12 females watch "K&K".
(i) FInd the probability that a person chosen at random from the group is either female or watches "K&K" or both.

I tried:
12/30 + 16/30 - 3/12 = 0.6833 but the answer is 5/6 = 0.833

anyone?????

 

[manya]

In a group of 30 teenagers, 13 of the 18 males watch "K&K" on TV and 3 of th 12 females watch "K&K".
(i) FInd the probability that a person chosen at random from the group is either female or watches "K&K" or both.

I tried:
12/30 + 16/30 - 3/12 = 0.6833 but the answer is 5/6 = 0.833

anyone?????

(12-3)/30 + (16-3)/30 + 3/30 = 5/6

 

[lemonrsiow]

(i) Deng wishes to test whether a certain coin is biased so that it is more likely to show Heads than Tails. He throws it 12 times. If it shows Heads more than 9 times, he will conclude that the coin is biased. Calculate the significance level of the test.

(ii) Deng throws another coin 100 times in order to test, at the 5% significance level, whether it is biased towards Heads. Find the rejection region for this test.

Question ii
My Approach

HNull: p=0.5

HAlt: p>0.5 where p= Heads

X- B(100, 0.5) is approximated to Y-N(50,25). At 5%, 1 tail so Z=1.645

To find the rejection region: (x-50)/(sqrt(25) = 1.645

In (x-50)/(sqrt(25) = 1.645, how do I apply the continuity correction? What I don't know is whether it should be x-0.5-50 or x+0.5-50.

Usually for these questions I usually approximate from P(X< x) => P(Y< x-0.5) so I know whether to add or minus 0.5, but for this question I'm a bit lost.