Mathematics: Post your doubts here!

[noor sajid]

A)
Prob = combinations with tracey and albert/all combinations

Two possible groups according to the rules:
5M1W and 4M2W
all combinations = (10C5)(9C1) + (10C4)(9C2) = 9828

5M1W
One women and one man are chosen, that leaves 4 men to be chosen from 9 men.
That gives us 9C4 combinations

4M2W
One women and one man are chosen, that leaves 3 men to be chosen from 9 men and 1 women to be chosen from 8 women.
That gives us (9C3)(8C1) combinations

Combinations with albert and tracey= 798
Prob = 798/9828

B)
N(either but not both) = N(tracey no albert) + N(albert no tracey)

N(tracey no albert) = N(5M1W with tracey no albert) + N(4M2W with tracey no albert)
N(albert no tracey) = N(5M1W with albert no tracey ) + N(4M2W with albert no tracey )

Using the same logic as in A:
N(tracey no albert) = (9C5) + (9C4)(8C1)
N(albert no tracey) = (9C4)(8C1) + (9C3)(8C2)

N(either but not both) = 4494

Thankyou so much!

 

[Hamnah Zahoor]

61/May/june/2014
Can anyone help me solve this question!

 

[A*****]

61/May/june/2014
Can anyone help me solve this question!

View attachment 64562

Here u go!

 

[A*****]

STATS (Can someone help?)
The random variable X has the distribution B (20,p)
Given that p=0.7 and P(X≥x) >0.1, find the greatest possible value of x.
Is there a straight forward method rather than the long method of trying?

The answer is 17 just in case.
Thanks

Which year is this from?

 

[Hamnah Zahoor]

Here u go!

Thanks a Lot!!

 

[Shemyaa]

Which year is this from?

I'm sorry I forgot. I believe its somewhere between 2005 and 2008.
It is not straight forward you literally have to calculate the probability and you can't use normal distribution concept but actually they kind off gave you a hint, the part before it they asked to calculate the probability when X=16 and we got it greater than 0.1, and we know when you are powering a fraction the greater the power the lower the value so you could expect to start ahead with 17 )

 

[Khitan]

Help needed in 12 part a please solve it.
TIA

 

[Khitan]

Does anyone have Notes about rotation of complex number point when it is mulitiplied or divide by other complex number?

 

[A*****]

Does anyone have Notes about rotation of complex number point when it is mulitiplied or divide by other complex number?

Which paper component is it from?

 

[Khitan]

Which paper component is it from?

Paper 3 MATHS ALEVEL.

 

[A*****]

Paper 3 MATHS ALEVEL.

I didn't see it in the syllabus...anyways if you find them plz share

 

[A*****]

Someone plz post the solution to the (ii) part

 

[Shemyaa]

Actually its an olevels question but i wasnt getting answer in o level thread so i decided to ask it from a level thread members
i hope no one minds it ::)))))))
help me with part b and part c of this question :

Okay, first of all, keep in mind the fact that they are similar
Use this concept:
(CY / CO) = (BY / BA )
They said the ratio of CB: BY is 1:2, therefore, you can say that CB magnitude is 1/3 of CY )
I kept getting AB as 2c instead of 4c
I took 0607 last year and you take another code, check if you have any extra rules I probably didn't take
Or you can take OAB and OBC since they're similar too
you can say (AC /OB)=(3a /AB) which you'll also get 2c
or even if you use (3a= kAB) and (6c=kBC) you'' get the same value.
Please check with what I'm saying and tackle this., the thing is its no isosceles or equilateral so we cant assume anything

 

[Shemyaa]

Okay

Actually its an olevels question but i wasnt getting answer in o level thread so i decided to ask it from a level thread members
i hope no one minds it ::)))))))
help me with part b and part c of this question :

so lets look at this
It might seem confusing if youre stressed because thats what happened to me
They clearly said ratio or CB:BY is 1:2 therefore we can say that BY is 2/3 of CY
so you can say
(CY / CO)= (BY / BA)
Since BY is 2/3 of CY then
(CY / CO)= (2/3CY / BA)
Reconstruct the formula to get (CY/ 2/3 CY)= (OC / BA)
So 3/2 =(-6c = BA)
BA- -4c
and since they want AB then reverse the direction so it becomes AB=4c
When you find AB you can find OB since AB= OB=OA
And you can find the rest using the same concept
DO NOT ASSUME ANYTHING THIS IS A SCALENE TRIANGLE NO SIDES ARE EQUAL SO NO VECTORS ARE EQUAL

 

[noor sajid]

Measurements of wind speed on a certain island were taken over a period of one year. A box-and-
whisker plot of the data is obtained where the LQ= 39 and UP=63. It is suggested that wind speed can be modelled approximately by a normal distribution with mean μ and standard deviation σ.
(i) Estimate the value of μ.
(ii) Estimate the value of σ.


The value of μ=(63+39)/2=51, but can someone help me how to find the σ?

 

[hellodjfos;s'ff]

Measurements of wind speed on a certain island were taken over a period of one year. A box-and-
whisker plot of the data is obtained where the LQ= 39 and UP=63. It is suggested that wind speed can be modelled approximately by a normal distribution with mean μ and standard deviation σ.
(i) Estimate the value of μ.
(ii) Estimate the value of σ.


The value of μ=(63+39)/2=51, but can someone help me how to find the σ?

Feeling lazy so won't solve it, just guide. You make any two equations and solve them simultaneously for example:
P(39<X<63)=0.5 - since the probability of values lying between LQ and UQ is 0.5 so solve this and get answer for standard deviation(using mean from (i))
You may also use the equations: p(X<39)=0.25 and P(X>63)=0.25 and solve simultaneously.

 

[hellodjfos;s'ff]

Someone plz post the solution to the (ii) part

|z-10i|=2|z-4i|
(z-10i)(z+10i)=4(z-4i)(z+41) - using the concept from first equation in (i)
(z-10i)(z-10i)*=4(z-4i)(z-4i)* - now use concept from 2nd equation in (ii)
(z-10i)(z*+10i)=4(z-4i)(z*+4i)
zz*+10iz-10iz*+100=4(zz*+4iz-4iz*+16)
3zz*+6iz-6iz*-36=0
3(zz*-2iz*+2iz-12)=0 - first part proven
|z-2i|=(z-2i)(z*+2i)=zz*-2iz*+2iz+4
Now compare this with the earlier equation we have proven. If we subtract 16 from this new equation, both the equations would be equal right? So...
zz*-2iz*+2iz+4=4^2 - notice i out 4^2 not 16 because we were squaring both sides of the equation as the question had told us to do earlier.
Hence radius=4 making the equation |z-2i|=4

 

[Hamnah Zahoor]

Can someone help me with Part (ii)

Oct/Nov/2016/61

 

[Hamnah Zahoor]

Part b(ii)

 

[Hamnah Zahoor]

|z-2i|=(z-2i)(z*+2i)=zz*-2iz*+2iz+4
Now compare this with the earlier equation we have proven. If we subtract 16 from this new equation, both the equations would be equal right? So...
zz*-2iz*+2iz+4=4^2 - notice i out 4^2 not 16 because we were squaring both sides of the equation as the question had told us to do earlier.
Hence radius=4 making the equation |z-2i|=4

Can you please explain this part again? I don't get the concept of 4^2 ?