statistics
posted by steven .
slot machines are now video games, with outcomes determined by random number generations. in the old days, slot machines were like this: you pull the lever to spin 3 wheels; each wheel has 20 symbols, all equally likely to show when the wheel stops spinning; the three wheels are independent of each other. suppose the middle wheel has 9 cherries among its 20 symbols, an the left and right wheels have one cherry each.
you win the jackpot if all three wheels show cherries. what is the probabiity of winning the jackpot?

The probability of a cherry on each of the two wheels = 1/20, while the middle wheel = 9/20.
The probability of all events occurring is found by multiplying the probability of the individual events.