posted by Stuck .
"In vase A, there are 3 red balls and 5 white balls. In vase B, there are 6 red balls and 4 white balls. Two balls are to be drawn at random, without replacement, from each vase. What is the probability of selecting 4 red balls?"
So I thought about doing 4 cases and then adding them up (don't pick red ball in A, don't pick red ball in B...pick red ball in A, pick red ball in B...etc...).
I did this:
But it doesn't work. What am I doing wrong?