Five defective mangoes are accidentally mixed with 15 goods ones. Four mangoes are drawn at random from this lot. Find the probability distribution of the number of defective mangoes.
X represents the number of defective mangoes drawn.
∴ X can take values 0,1,2 or 3
∵ there are total 20mangoes (15good+5defective) mangoes
n(S) = total possible ways of selecting 5 mangoes = 
P(X = 0) = P(selecting no defective mango) = 
P(X = 1) = P(selecting 1 defective mango and 3 good mangoes)
= 
P(X = 2) = P(selecting 2 defective mangoes and 2 good mangoes)
= 
P(X = 3) = P(selecting 3 defective mangoes and 1 good mango)
= 
P(X = 4) = P(selecting 4 defective mangoes and no good mango)
= 
Now we have pi and xi.
Following table represents the probability distribution of X :
