These problems seem so easy or am I just tricked by the wording?
1). You visit the home of an acquaintance, who says, "I have two kids." A boy walks into the room. The acquaintance says, "That's one of my kids." What is the probability that the other one is a boy?
2). You live in a culture where, when children are introduced, male children are always introduced first, in descending order of age, and then female children, also in descending age order. You visit the home of an acquaintance, who says, "I have two kids, let me introduce them." He yells, "John come here." (John is a boy's name). What is the probability that the other child is a boy?
3). You go to a parent-teacher meeting. The principal is sitting in the first row. You've heard that the principal has two children. The teacher in charge asks everyone who has a son (meaning at least one) to raise a hand. The principal raises her hand. What is the probability that the principal has two sons?
In the three problems, assume that a child is equally likely to be male or female and that the sex of one child in a family is independent of the sex of any other children in that family.
I'm getting really tricked by the wording, it seems to me that the answer to all of them is 1/2 but that's not the case for all three of them.