1. The problem statement, all variables and given/known data I don't know how to ask my question without an example, so I am giving an example here. For example, if there are 100 tables in a restaurant where 50 of them are for smoking while 50 of them are for non smoking. If two tables are chosen successively without replacement, then what is the probability of getting one tables for smoking and one for non-smoking? 2. Relevant equations 3. The attempt at a solution P(required) = P(1st smoking)xP(2nd non smoking) + P(1st non smoking)xP(2nd smoking) = 50/100 x 50/99 + 50/100 x 50/99 Is it correct? I am not sure. I remember some boooks saying that "probability has no order", I don't understand what it means actually.