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Probability of selection 190 - 2 member groups

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Probability of selection 190 - 2 member groups

by ELYAC Realty » Tue Sep 02, 2008 9:28 pm
This is a probability (factorial) question.
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by loki.gmat » Tue Sep 02, 2008 9:40 pm
assume that there r n members in the club.
from the data we have
nC2=190
n!/2!(n-2)!=190
n(n-1)/2=190
n(n-1)=380
for n=20
20(20-1)=380.

hence IMO A.


Thanks!
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by ELYAC Realty » Tue Sep 02, 2008 9:46 pm
loki.gmat wrote:assume that there r n members in the club.
from the data we have
nC2=190
n!/2!(n-2)!=190
n(n-1)/2=190
n(n-1)=380
for n=20
20(20-1)=380.

hence IMO A.


Thanks!
Im new to this forum, what does "nC2" and "IMO" stand for?
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by ELYAC Realty » Tue Sep 02, 2008 9:57 pm
n!/2!(n-2)!=190
n(n-1)/2=190

Can you explain how you went from the first equation to the second? Thanks
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