SOLUTION: 400 families were surveyed. It was found that 90% had a TV set and 60% had a computer. Every family had at least one of these items. One of the families is randomly selected, and i

Algebra ->  Probability-and-statistics -> SOLUTION: 400 families were surveyed. It was found that 90% had a TV set and 60% had a computer. Every family had at least one of these items. One of the families is randomly selected, and i      Log On


   

Question 848131: 400 families were surveyed. It was found that 90% had a TV set and 60% had a computer. Every family had at least one of these items. One of the families is randomly selected, and it id found that they have a computer. Find the probability that it also has a TV set.
Answer by stanbon(75887) About Me  (Show Source):
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400 families were surveyed. It was found that 90% had a TV set and 60% had a computer. Every family had at least one of these items. One of the families is randomly selected, and it id found that they have a computer. Find the probability that it also has a TV set.
union = # with computer + # with TV - # with both
400 = 0.9*400 + 0.6*400 - # with both
400 = 360 + 240 - # with both
# with both = 200
P(computer AND TV) = 200/400 = 1/2
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P(TV | computer) + P(TV and computer)/P(computer) = 0.5/0.6 = 5/6
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Cheers,
Stan H.