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2. Ben takes
2 hours to wash 500 dishes, and Frank takes 3 hours to wash 450
dishes. How long will they take, working together, to wash 1000
dishes? Well, Ben can do 250 dishes per hour, and Frank can do
150 dishes per hour. Working together, they can do 250 + 150 =
400 dishes an hour. Then, fairly obviously, it will take two and
a half hours for the two of them to wash 1000 dishes.
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Answer
= _________________
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4. When I
visit the local library, the probability that someone is reading
the current issue of Sports Illustrated is 0.4, the probability
that someone is reading Time is 0.3, and the probability that
at least one of these two magazines is being read by someone is
0.5. What is the probability that neither of the two is being
read?
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Answer
= _________________
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