company A has 110 employed, company B has 750 employed and company C has 250 employed. Compute the probability that an employee selected at random comes from company A or B.

Answer 1

Size of set A = |A| = 110,
similarly |B|=750, |C|=250
Size of Ω, sample space, S = |A|+|B|+|C|=1110

Random selection from equi-probability sample would be
P(A or B)=P(A)+P(B)=(|A|+|B|)/S