5E practice problems for exam 1
1. A total of 500 married working couples were polled about their annual salaries, with the following
information resulting.
Husband
Wife
Less than $75,000
More than $75,000
Less than $75,000
212
198
More than $75,000
36
54
Thus, for instance, in 36 of the couples the wife earned more and the husband earned less than $75,000.
One of the couples questioned is to be chosen at randomly.
(a) What is the probability that the husband earns less than $75,000?
(b) Find the probability that the wife earns more than $75,000 given that the husband earns more than
this amount?
2. Bill has two old cars, a Pontiac and a Honda. At this point, neither is very reliable. Let .75 be the
probability that he arrives to work without car problems when he drives the Pontiac, and let .60 be
the probability that he arrives to work without car problems if he takes the Honda. Because Pontiac is
more reliable, Bill chooses to drive Pontiac to work with probability .80.
What is the probability that tomorrow Bill
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 Fall '08
 LANDRIGAN
 Probability, Standard Deviation, Mean, Automobile, Dice

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