I was just wondering, how do you calculate the probability of something if you draw a lot of them together at the same time? For example: there are 10 red balls, 10 blue balls and 10 green balls. You put your hands in and draw out 3 balls at the same time. How would you calculate the probability of getting 2 balls of the same color and 1 ball of different color at the same time? I know how to calculate if they're taken out slowly 1by1 with or without replacement, but I have no clue how to do this.