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Helen and Patty both belong to a club of 25 members. A committee of 4 is to be selected at random from the 25 members. Find the probability that both Helen and Patty will be selected.

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Guest Apr 9, 2017
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We are just countng sets, here......

 

The total possible sets  formed from choosing 4 members from 25  is C(25,4)  = 12650

 

However.......we are only interested in the sets that contain both Helen and Patty......so.....we want to choose any 2 other members from the remaining 23  = C(23,2)  = 253

 

So....the probability that both Helen and Patty  are chosen  =  253 / 12650 =

1/50  = .02  =   2%

 

 

cool cool cool

CPhill  Apr 9, 2017

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