
Andy C. answered 05/10/18
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Math/Physics Tutor
Probability of at least once is the same is
1 - Probability of NONE at all
It is binomial, p=5/19, N=4, k=0, with formula (N choose k)* p^k * (1-p)^(N-k)
So to calculate the probability that it will not happen in four years,
we first note that the first two terms in the formula, namely the
combinatoric (4 choose 0) AND (5/19)^0 are both equal to 1
The probability is then (14/19)^4 <--- it will not happen for 4 years in a row
= 38416/130321 = 0.294779813....
The final answer is then:
91815/130321 = 0.704529585.... or ALMOST 70.5%
So chances are we are gonna get hit ;-)