that the number of students who fail math follows a binomial distribution, for a class
of nine students, calculate
(i) the variance for the number of persons who failed math in the class
(ii) the probability that exactly two students failed math
(iii) the probability that at least three students failed math.
(ii) P(X=2) can do on a calculator or use formula nCr(p^r)(1-p)^(n-r)
(iii) P(X>=3) = 1 - P(X<=2) since X is discrete variable.