Question 393165
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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(taking the bus)= .45 & q = .55
nCx = {{{n!/(x!(n-x!))}}}
P(out of 4, at least one takes bus) = 1-P(none taking bus) = 1 - (.55)^4
P(out of 4, at least one takes bus) = 1 - (.55)^4 = 1 - .0915 = .9085