Shane O'Brien received an email from a man named James Taylor, who claims he can predict the results of NFL games. The e-mail says: “July 22, New York Giants win against the Dallas Cowboys”.
Shane does not think much about the e-mail, but when the day of the game arrives he realizes that the Giants actually beat the Cowboys.
Shane gets eight more e-mails with correct predictions of the games in the NFL. But the tenth
e-mail he receives is different. The e-mail says: "To receive the prediction of the result of the next NFL game, deposit $ 100 into this account."
Shane thinks a little and sees he could make two thousand U.S. dollars in a gambling house, then it would be worthwhile, but soon after depositing the money in the account of James Taylor, he realized that he had been cheated and that James would not know who would win the game.
What did Shane discover?
HINT: He remembered a mathematical fact, which involved probability.