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Old 08-03-2007   #1
Christine T
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A batch consists of 12 defective coils and 88 good ones. Find the probability of getting two good coils when two coils are randomly selected if the first selection is replaced before the second is made?
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Old 08-03-2007   #2
ricanthuglyp
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think its 7
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Old 08-03-2007   #3
Arash
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It's very easy. There are totally 12+88=100 coils in the batch. So the probability of getting a good coil at the first time is 88/100=0.88 . Because you replace the first selection before taking the second one, the probability of getting another good coil is the same as the first one (88 percent). Therefore, the probability of getting two good coil is equal to 0.88 x 0.88 = 0.7744 or 77.44%.
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