Mathematics: Post your doubts here!

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well if ur asking from me............i am not giving the paper of stats ... AS maths + stats in 2012 june........

NEED HELP IN PERMUTATIONS AND COMBINATIONS!!!!
 

XPFMember

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Assalamoalaikum!!

For permutations and combinations watch this whole series of the tutorial, and you're good to go! ;) http://www.examsolutions.co.uk/maths-re ... rial-1.php


I see people finding permutations and combinations hard, but honestly i enjoy it a lot..

And one more thing, (you may understand this better may be after you've gone through the topic, but anyways)
to make out when you have to use permutation (nPr of the calculator) and when to use combinations (nCr) , checck if the different arrangements of the selections will make any difference or not...if it does then you've to use nPr, and if it doesn't then u must use nCr.

Eg. lets say I want to choose two numbers from a total of three..how many possible selections are there?

now see i may choose 1 2 ; 1 3 ; 2 3
now the no. i've chosen can be written as 2 1 ; 3 1 ; 3 2

and obviously, this is giving me different numbers, so here arrangement does matter..so go for nPr => 3P2 = 6

but say if i got to chose 2 people from a total of 3 (A, B and C)

so possibilities are A B ; A C ; B/ C
and if i make this as B A ; C A ; C B
it doesn't make any difference as in the end there are the same people whether A first or B first....so that means arrangement does not matter...we'll use nCr => 3C2 = 3

P.S. These were pretty simple examples, I used them to explain the concept...you'll find this part of my explanation helpful when later on you tackle some more harder situations...this part really makes this thing easy...it did for me ;)
 
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ching293 said:
mrpaudel said:
ching293 said:
anyone please help :)

the first inequality is the inequality for the " perpendicular bisector of line joining (0,0) and (2,0)......whereas the 2nd inequality is for the " straight line starting from u making angle of pi/4 with the horizontal....!! now shade the common part..!!
the angle at point u looks like a or b?

I hope this will help...!! but a bit messy...sorry for that..!!
 

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m lazy one..so wrote it in degree...u have to write it in radian from the very first...!! i think u know it....anyways..!! i hope it helped..!!
 
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