Consider a more familiar sounding problem, which is exactly the same in terms of probability:
In an urn, there are 2 Red, 9 White, 3 Black, 1 Blue and 6 Brown marbles.
What is the probability of the first 2 picked marbles, being white, if we do dot replace the marbles.
i) the probability of the first pick to be white is 9/(2+9+3+1+6)=9/21=3/7
ii) the probability of the second pick to be white, after the first one was white is: (9-1)/(21-1)=8/20=2/5
The probability of the first 2 picks being white is (3/7)*(2/5)=6/35
Answer: 6/35
