Question

A bag contains 3 Red, 4 White, and 5 bye balls. All balls are different . Two balls are drawn at random. Probability that they are of different colour is?

Answer 1

If The same color balls are indistinguishable, then the sample space would be just { rr , ww, bb, rb, rw , bw }. (Note the probability of elements in the sample space here though are not same).

Since they are all different, we take the sample space to be (12 choose 2) . (See the previous solution).

The confusion may have occured as the answers for both cases are same.