Question: A tennis player makes a successful first serve 59% of the time. If she serves 7 tims, what is the probability that she gets exactly 3 first serves in? Assume that each serve is independant of the others.
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Answer: It follows binomial distribution with parameter p=59%=0.59, q=1-p=1-0.59=0.41 n=7 and r=3 we know P(X=r)=nCr*(p)^r *(q)^(n-r) So, P(X=r)=7C3*(0.59)^3*(0.41)^4=0.203(Ans.)   Edit