Off of my last ten pack I had 6 germinate and 4 were girls and two were boys. Not a great germ rate, but I have made one of my boys fuck one of my girls so I will have plenty of children for the future. Because we all know that "the children are the future".
I've heard that out of 10 seeds you should expect a 50% ratio of males to females. This actually played out in my last grow. I got exactly 5 females and 5 males out of 10 seeds.