420
Glitch in the matrix
(ani.social)
Be sure to follow the rule before you head out.
Rule: You must post before you leave.
You didn't eliminate BG and GB where a girl opens the door though. If you do that, then the answer is 50%. Because you remove half the probability from BG and GB and you remove none from BB.
I know you didn't eliminate those cases because you said "That leaves us with 3 possibilities with equal probabilities". That would be false, BB is twice as likely.
I'm guessing you haven't read the rest of the thread? My first comment was incorrect and the correction has been made.