Question 1118545: The probability that a battery will last 10 hr or more is 0.8, and the probability that it will last 15 hr or more is 0.12. Given that a battery has lasted 10 hr, find the probability that it will last 15 hr or more. (Round your answer to three decimal places.)
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! 80% of the batteries last 10 hours or more.
12% of the batteries last 15 hours of more.
if these probabilities hold, then, out of 1000 batteries produced, 800 of them will have lasted 10 hours or more and 120 of them will have lasted 15 hours or more.
the 120 that has lasted 15 hours or more must have lasted 10 hours or more, so they are part of the set that lasted 10 hours of more.
they are 12% of the total of 1000 batteries produced, but they are 15% of the 800 batteries that lasted 10 hours or more, because 120 / 800 = .15 = 15%.
the solution appears to be that 15% of the batteries that lasted 10 hours or more lasted 15 hours or more.
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