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Mathematics: Post your doubts here!

A

aleezay

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In p6 when scaling variables.. rq when the give u (x-50)^2 and ask you to calculate s.d of x... what formula do we use? S.dy = aS.dx or S.dy = |a|S.dx
where a is x's coefficient and y is x-50..
 
A

aleezay

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Zenia ZZ said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_61.pdf
please help me with(question 6 ii )
and for question 7 (a ii ) 7! x 7! (is for arranging the friends and the partners ) but we are multiplying by 2 because either the friends could be first or the partners ? am i right ?? i want to confirm .
Click to expand...
Yes you are.. for your first q, let me give you the main idea. If you still have trouble solving it, ill post the whole working :)
more than an s.d from the mean means: P(X<mean-s.d) + P(X>mean+s.d).. youll get the probability. Since expected number is no of trials x probability.. youll multiply your probability with 1000. Simple :)
PS= In such qs, round off your answer to 3sf and not a whole no, even though the q asks you to give the expected number of birds :)
 
Y

Yousif Mukkhtar

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Zenia ZZ said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_61.pdf
please help me with(question 6 ii )
and for question 7 (a ii ) 7! x 7! (is for arranging the friends and the partners ) but we are multiplying by 2 because either the friends could be first or the partners ? am i right ?? i want to confirm .
Click to expand...
Q6ii) Firs you need to find the probability of lengths more than one standard deviation from mean. To get this idea, imagine the STANDARD NORMAL DISTRIBUTION curve in which 0 is the mean. When it says more than one standard deviation from mean, it means more than +1 and -1 from the mean 0. See the attached image for better clarification.

When you get this idea then:
P(more than 1 standard deviation)= P(Z greater than 1) or P(Z less than -1)
=P(Z greater than 1) x 2 (as both sides are symmetrical)
=(1- fi(1))x2
=(1-0.8413)x2
=0.3174

Therefore number of feathers= 0.3174 x1000= 317 feathers
 

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Y

Yousif Mukkhtar

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Z

Zenia ZZ

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Jiyad Ahsan said:
part 3, sorry it took so much time
oh and i forgot to mention ( though its obvious)
the denominators cancel out a part of the numerators so only the 8P8 's are left
Click to expand...
Honestly you are so helpful . Thank a tonne for the help you are providing me :) May you pass with bright colours in all your exams ! Good Luck !
 
Anika Raisa

Anika Raisa

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Yousif Mukkhtar said:
Can anyone explain why they gave Z= 1.882 and p=0.97? Q5) I)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_61.pdf
Click to expand...
Jiyad Ahsan said:
part (i)
12P8
=19958400

part (ii)
so frances and mary do not sit together,
just find out the number of ways in which they DO sit together and subtract from the total
if they sit together then 11P7 x 2P2 - - - - (11P7 because since they sit together you count them as one unit, 2P2 because they can arrange themselves in their group, sit left or right)
11P7 x 2P2
=3326400
this is when they do sit together, so subtracting from total ( part (i))
19958400 - 3326400
=16632000

part (iii)
i'll just upload the working for it in a bit
"Jiyad Ahsan, post: 564620, member: 31829"]part 3, sorry it took so much time
oh and i forgot to mention ( though its obvious)
the denominators cancel out a part of the numerators so only the 8P8 's are left
Click to expand...

All credit to JiyadAhsan ....
 
Rutzaba

Rutzaba

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is this right?
jub < hota hai to direct table read krte hain
​
jub ≤ hota hai tou 1 se minus krte hain
​
jub > hota hai tou 1 se minus krte hain
​
jub ≥ hota hai tou direct lete hain
​
agar jo hum nikal rhe hain wo negative ho
​
tou 1 mai se minus krskte hain
 
1

19islandprincess96

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Rutzaba said:
is this right?
jub < hota hai to direct table read krte hain

​

jub ≤ hota hai tou 1 se minus krte hain

​

jub > hota hai tou 1 se minus krte hain

​

jub ≥ hota hai tou direct lete hain

​

agar jo hum nikal rhe hain wo negative ho

​

tou 1 mai se minus krskte hain
Click to expand...

P(z<a) = direct table
P(z>a) = 1- table value
P(z<-a) = 1 - table value
P(z>-a) = direct table value
P(a<z<b) = value of (b) from table - value of (a) from table
P(-a<z<b) = [value of (b) from table + value of (a) from table] -1
P(-a<z<-b) = Value of (a) from table - Value of (b) from table
 
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