Mr Jones has two children The older child is a girl What is

Mr. Jones has two children. The older child is a girl. What is the probability that both children are girls?

Mr. Smith has two children. At least one of them is a boy. What is the probability that both children are boys?

Solution

Two kids (1st then second): BB | BG | GB | GG

A) Mr. Jones has two children. The older child is a girl GB | GG

B) Mr. Smith has two children. Atleast one of them is a boy. BB | BG | GB

Probability that both children are boys is 1/3.