This is a question I read somewhere else and think so much about getting an answer, but still struggling. Here is the problem:
I have 9 virus which is 5 of them are good, and 4 of them are bad. Every time I kill a virus, it dies, and 2 viruses will be born from its body which is having 50-50 chances to be a good or bad virus.
What is the probability that after 100 times I kill a virus randomly and the amount of bad virus is zero? Which probability formula or theory should I learn to solve this one? Thanks.