Boy or Girl Riddle
You ask your friend Gillian has two children. You ask Gillian whether at least one them is a boy. She responds yes. Assuming the chance her having a boy and girl is 50/50. What is the chance that she has 2 boys? 1 in ?
Go over all the possibilities.
1/3. There are four combinations that she produce offsprings. Boy/Boy Boy/Girl Girl/Boy Girl/Girl Since the last combination is not possible . Than leaves a one in three chance that it is boy/boy.