itsabhishekgupta
Can we interpret in the following way?
It shouldnt matter whichever animal he takes out in the first time - implies probability is 1.
What matters really is the second animal that he chooses.
As he has already chose 1 animal, so the remaining animals are 4. Hence whichever animal he pulls out will make a matched pair with the first chosen animal. Therefore the probability should be 1/4 or 25%
Whats wrong with this approach?
I think I understand why you may think this, especially if you have done similar questions like these, but with one subtle but important difference - the things here are different, with different respective quantities.
e.g. if this was say, 5 pairs of ducks (Male-female), you could then use your approach.
P(of choosing first) = 1 and then the other one to compare the pair would be 1/9, so total would be 1*1/9 = 1/9
Here it does not matter which couple you pick it from, unlike the one in the question.
However, since these are different things in the given question, their starting cases cant be considered as the same (3 vs 2) and thus you have to take each one as a standalone case (DD and RR).
Hope this helps resolve the confusion