Question 1160252
p = .4
q = 1 - p = .6
n = 20
p(x) = p^x * q^(n-x) * c(n,x)
this is the binomial probability formula you would use to solve this problem.
the probability that it entered at least 1 computer is equal to 1 minus the probability that it entered 0 computers.
p(0) = .4^0 * .6^20 * c(20,0) = 3.65615844 * 10^-5.
1 minus that = .9999634384.
that's your answer.
you can use your calculator to confirm.
all the probabilities, given n = 10, p = .4 and q = .6 are shown below.
the sum of all probabilities is equal to 1, as it should be.
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