Question 464956
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Hi,
Note: The probability of x successes in n trials is: 
P = nCx* {{{p^x*q^(n-x)}}} where p and q are the probabilities of success and failure respectively. 
In this case p= .70 and q = .30
nCx = {{{n!/(x!(n-x)!)}}}
P(at least one in four) = 1 - P(none)
                              P(none) = .30^4
P(at least one in four) = 1 - .30^4 = .9919