stats please help

[Madiha :)]

can anyone please xplain q6iv of this paper
http://www.xtremepapers.me/CIE/Internat ... _qp_61.pdf

 

[ahmed t]

you already found out 4 different colours and 3 diff colours
all u do now is find 2 different colours and add up previous results
for 2 different cols u must pick two colours out of six and arrange these 4 pegs
so it will be
6C2 *4!/2!2!
that will give you 90 add up with the rest

 

[Madiha :)]

no no .. i want to knw how to find out 3 different colours ?>

 

[ahmed t]

oh then it will either be
2R and 2 other colours
or 2G and 2 other colours
so for each colour u must pick another two colours
so it will be 5C2 (since we already pickked one colour to be used twice)*6
then we must include arrangement wich will be 4!/2! 2 colours will be the same
times it all together we get 720

 

[Madiha :)]

yar m really sorry but i dnt understnd .. y did u take 5C2 ?

 

[ahmed t]

well u take one of the six colours twice, then you must pick another 2 pegs but they must be of different colours.
so there will be 5 colours and u must pik 2 of them along with the other 2 same coloured pegs, thats how you get 5C2

 

[Madiha :)]

oh oh okkay thanku=)

 

[ahmed t]

no problemo