FCPP 3: The Flippant Juror

This is the solution to problem 3 from Fifty Challenging Problems in Probability by Frederick Mosteller (1987). The problem is paraphrased below; for reference, it is inspired by the original book. Jury A consists of three jurors. The first two have a probability \(p\) of being correct. The third one chooses based on a fair coin toss. All three jurors vote independently. Jury B consists of a single juror that is correct with probability \(p\). ...

January 1, 2026 · 3 min · David Nabergoj

FCPP 2: Successive wins

This is the solution for problem 2 from Fifty Challenging Problems in Probability by Frederick Mosteller (1987). The problem is paraphrased below; for reference, it is inspired by the original book. Ellis is a tennis player who has to compete against two players: his father and the tennis club champion. The champion is a better player than the father. Ellis will play a three-set series with alternating opponents. He can either play his father first, then the champion, then his father again; or the champion first, then his father, then the champion again. If he wins two sets in a row, he wins a special prize. ...

December 30, 2025 · 3 min · David Nabergoj

FCPP 1: The Sock Drawer

This is the first post in a series solving problems from Fifty Challenging Problems in Probability by Frederick Mosteller (1987). The problem is paraphrased below; for reference, it is inspired by the original book. A drawer contains some red and black socks. Two socks are drawn at random, and the probability that both are red is \(1/2\). What is the minimum total number of socks? What is the minimum if the number of black socks is even? Let’s dive in! ...

December 30, 2025 · 6 min · David Nabergoj