Math (expected value)
posted by Anna on .
A roulette wheel in Las Vegas has 18 red slots and 18 black slots numbered alternately with the numbers 1 through 36. Two green slots are numbered 0 and 00. The winning number is determined by the slot into which a single marble rolls. Players are not allowed to bet on green. The house wins all bets if 0 or 00 comes up. A $1 bet on a single roll of a roulette wheel wins $36 if the marble lands in the slot for the number selected. If that number doesnâ€™t come the person placing the bet loses the $1. What is the expected value of such a bet?

expected value= reward*probability
= 36* 1/38 (ie, he has one chance in 38 to win, with a reward of 36)