SOLUTION: 30% of the people that get mail-order catalogs order something. Find the probability that only two of 9 people getting these catalogs will order something.

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Question 375355: 30% of the people that get mail-order catalogs order something. Find the probability that only two of 9 people getting these catalogs will order something.
Found 2 solutions by Fombitz, ewatrrr:
Answer by Fombitz(32388) About Me  (Show Source):
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi,

Note: The probability of x successes in n trials is: 

.

P = nCx* p%5Ex%2Aq%5E%28n-x%29 where p and q are the probabilities of success and failure respectively. 

In this case p = .30 & q = .70

nCx = n%21%2F%28x%21%28n-x%29%21%29%29

9C2 = 9%21%2F%282%21%287%29%21%29%29 = 36

P(2) = 36(.30)^2(.70)^7 = .2668