6.5.5 A doctor studies the known cancer patients in a certain town.
The probability that a randomly chosen resident has cancer is found to
be .001. It is found that 20% of the town works for Ajax Chemical Company.
The probability that an employee of Ajax has cancer is equal to .003.
Are the events "has cancer" and "works for Ajax" independent of one another?

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6.5.8 A stereo system contains 50 transistors. The probability that a given
transistor will fail in 100,000 hours of use is .0005. Assume that the
failure of the various transistors is independent of one another. What is
the probability that no transistor will fail during the first 100,000 hours
of use?


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6.6.16 Two balls are selected at random from an urn containing two white
balls and 3 red balls. What is the conditional probability that both
balls are white given that at least one of them is white. 
(Cf Example two!)