[ig06]

Thanks Jay :-) I think Siegmund's solution is neater though because its so simple. I understand he is saying for each element there is a probability of 1/2 that it is in A and a probability 1/2 its in B. Hence there is a probability of 1/4 that it is in A but not in B thereby precluding the possibility that A is a subset of B. Since there are n elements in S, the probability that A is a subset of B is therefore (3/4)^n. Nice solution too :-)