A gambler's losing streak accidentally invented the mathematics of probability
In the 1650s, French gambler Chevalier de Méré bet on rolling at least one 6 in four rolls of a die (which he consistently won) and on rolling double-6 in twenty-four rolls of two dice (which he consistently lost) — even though he'd scaled the odds up the same way for both bets. Why did one bet make him money and the other cost him?
Reveal the answer
The two bets aren't equally likely: the probability of at least one 6 in four rolls is about 51.8%, while double-6 in twenty-four rolls is about 49.1% — close, but not equal, so his simple 4:6::24:36 scaling was wrong. Puzzled, de Méré wrote to Blaise Pascal, whose resulting correspondence with Pierre de Fermat in 1654 helped lay the foundations of modern probability theory.
— Blaise Pascal, Correspondence with Pierre de Fermat — 1654