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Urgent: Maths CIE Stats

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$!$RatJumper$!$:

--- Quote from: Deadly_king on October 29, 2010, 04:48:45 pm ---I can't really explain the workings from the marking scheme but I did it another way which was approved by my teacher.

First we find out the number of arrangements in which all the 9 persons can be arranged. This will be (9! +(7! x 3!))
9! => There are nine persons which can be arranged in any way.
(7! x 3!) => There are 6 men and 3 women. We'll be taking all the women to be standing beside each other. Hence they are taken as one possiblity only which makes 7!. The 3 women can then be arranged in any way 3!.

Then we need to find the number of arrangements in which two women are next to each other => 3(8! x 2!)
8! = > One woman is taken as one possiblity and the other two as another possiblity. In all there will be 8 possiblities, after adding the six men.


Number of arrangements : (9! +(7! x 3!)) - 3(8! x 2!) = 151200

Hope you understand :)

--- End quote ---

Good job!

Deadly_king:

--- Quote from: $!$RatJumper$!$ on October 29, 2010, 05:31:58 pm ---Good job!

--- End quote ---

Glad to have been of help :)

I just hope cs understands it as well ;)

cs:
yea. there's working behind my pass year book, and they gave 2 types of working, i did the way you did, and manage to get 9! and 7!X3!, i don't get this part(when two women are together):

Then we need to find the number of arrangements in which two women are next to each other => 3(8! x 2!)

I got 8! X 2!, why is there a 3?

Deadly_king:

--- Quote from: cs on October 30, 2010, 01:47:01 am ---yea. there's working behind my pass year book, and they gave 2 types of working, i did the way you did, and manage to get 9! and 7!X3!, i don't get this part(when two women are together):

Then we need to find the number of arrangements in which two women are next to each other => 3(8! x 2!)

I got 8! X 2!, why is there a 3?

--- End quote ---

The three is because there are three women ;)

Let there be 3 women : W1, W2 and W3

Possible arrangement are :
i) W1W2 and W3
ii) W1W3 and W2
iii) W2W3 and W1

So there are 3 ways in which the women could be arranged :D

S.M.A.T:
DK son 8)............u r awesome 8).................+rep

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