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Mathematics: Post your doubts here!

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saadgujjar

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plz explain q 3(ii)....i dont know any formula of solving this...if possible plz share any link
and also explain q4 (iii)upload_2014-5-15_5-55-29.png
 
ZaqZainab

ZaqZainab

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saadgujjar said:
plz explain q 3(ii)....i dont know any formula of solving this...if possible plz share any link
and also explain q4 (iii)View attachment 42598
Click to expand...
well there is no formula
they have given you
sum of (x-45)=-148 and sum of (x-45)^2=3089
you have 36 values
but now they added 1 other value which is 29
so that makes it -148-45+29
as for the square 3089+(-45+29)^2
 
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_Ahmad

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ZaqZainab said:
yup me
Click to expand...
A general question.
In CF questions they give data in a table as (x < 40 or <10 or as ≤100)
For finding mean we need to convert this data into a interval which will start sometimes from (0-9) or (1-9)
so can u please tell when to start from 0 and when from 1

Hope you got my question
if you need some questions I can send you link
 
ZaqZainab

ZaqZainab

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_Ahmad said:
A general question.
In CF questions they give data in a table as (x < 40 or <10 or as ≤100)
For finding mean we need to convert this data into a interval which will start sometimes from (0-9) or (1-9)
so can u please tell when to start from 0 and when from 1

Hope you got my question
if you need some questions I can send you link
Click to expand...
tbh i didnt get it what do you mean by (0-9)??
a question would be better
 
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_Ahmad

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ZaqZainab
Click to expand...
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s13_qp_63.pdf Q6 (iii)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s11_qp_63.pdf Q3 (iii)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s11_qp_61.pdf Q6 (iv)

In these above listed questions for finding mean we make intervals. So can you please tell how to make intervals in these questions.
 
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saadgujjar

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ZaqZainab said:
well there is no formula
they have given you
sum of (x-45)=-148 and sum of (x-45)^2=3089
you have 36 values
but now they added 1 other value which is 29
so that makes it -148-45+29
as for the square 3089+(-45+29)^2
Click to expand...
still don't understand...can u solve it on paper and send photo plz?explain the other question also
 
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_Ahmad

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saadgujjar said:
still don't understand...can u solve it on paper and send photo plz?explain the other question also
Click to expand...

In the first part (for 36 values)
Σ(x − 45) = −148 and
Σ(x − 45)^2=3089

Now for finding sd of 37 values we need new Σ(x − 45) and Σ(x − 45)^2
x=29

(x-45)=29-45=-16
so new Σ(x − 45)= -148+(-16)=-164

(x-45)2=(29-45)^2=256
So new Σ(x − 45)^2 =256+3089=3345

now you got new values of Σ(x − 45) and Σ(x − 45)^2
so just apply the formula of sd to get the answer

Hope you got it
 
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