One Girl - One Boy in New Logic/Math Puzzles Posted August 30, 2007 · Report reply A friend insisted the answer "had to be" 50%. So I asked him this: Of all the couples in the world with 2 children, statistically speaking, what fraction have a 1 boy and 1 girl? He answered: one half. and what fraction have 2 boys and 0 girls? He answered: one fourth. So, just taking these couples, what fraction have 2 boys and 0 girls? He answered: One third; and then: Oh.... OK I get it now.