What are the chanches that the other ball he has drawn out is also Yellow?

Question

This is a famous paradox probability riddle which has caused a great deal of argument and disbelief from many who cannot accept the correct answer.

Four balls are placed in a bowl. One is Green, one is Black and the other two are Yellow. The bowl is shaken and someone draws two balls from the bowl. He looks at the two balls and announces that atleast one of them is Yellow.
What are the chanches that the other ball he has drawn out is also Yellow?

Answer 1

20%
.
There are 12 possible combinations (order is important):
Y1-Y2, Y1-G, Y1-B
Y2-Y1, Y2-G, Y2-B
G-Y1, G-Y2, G-B
B-Y1, B-Y2, B-G
Of these combination 2 are not valid (G-B and B-G).
This leaves 10 combinations. Of these combinations 2 have both yellow balls.
Thus the chance that the other ball is also yellow is 2/10 = 20%.