Tim Ricchuiti on Instagram: "The Counterintuitive Math Behind the Boy Born on Tuesday Problem This probability brain-teaser is counterintuitive. Imagine someone has two children. What are the chances at least one is a girl? If one child is a boy born on a Tuesday, it changes the probability. Consider Mary with children. If she has one child, the chance of a girl is 50%. With two, it’s 75%; with three, 87.5%. More children mean a higher chance of at least one girl. For two children, the sample sp