Maths Week Puzzle 6

The Chevalier De Mere was not actually a nobleman

The Chevalier De Mere was not actually a nobleman. He was a 17th century French writer and liberal thinker who is remembered nowadays because he unwittingly was responsible for that important branch of mathematics, probability. He was fond of gambling and would offer even money bets that he would throw at least one six in four rolls of a die. He found that over a sufficient number of games that he was always ahead.

His friends must have noticed this too, because he switched to offering a bet that he would throw a double six on 24 rolls of two dice. He reasoned that for every throw of one die there were six numbers that could pop up on the second die, so therefore one would need six times as many throws with this bet.

However, he found that he was falling behind with this bet and supposedly enlisted the help of his friend, the brilliant Blaise Pascal, to explain why. Pascal, one of the most brilliant minds in history, figured it out, leading to the mathematics of probability that has a huge influence on our lives. It is used to predict chance in everything from casinos to your life insurance. Can you figure out why the Chevalier was losing?

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The odds of getting one six from four throws of a die is slightly more than 50:50, so over enough games the Chevalier would keep ahead. However, the odds of throwing a double six in 24 throws is slightly less than 50:50. See mathsweek.ie/2012/irishtimes for details of how to solve the puzzle