A person buys a lottery ticket in 50 lotteries, in each of which his chance of winning a prize is 1/100. What is the probability that he will win a prize
(a) At least once
(b) Exactly once
(c) At least twice?
(a) In this question, let X represents the number of prizes winning in 50 lotteries and the trials are Bernoulli trials
Here clearly, we have X is a binomial distribution where n = 50 and 
Thus, 
∴ 
Hence, probability of winning in lottery atleast once 
= 1 – P (X <1)
= 1 – P (X = 0)
(b) Probability of winning in lottery exactly once 
(c) Probability of winning in lottery atleast twice 
= 1 – P (X < 2)
= 
10