SOLUTION: In a box of thrity aaa batteries there are three defective batteries. Two batteries are randomly selected and tested. What is the probability that both are defective, if the first

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Question 433286: In a box of thrity aaa batteries there are three defective batteries. Two batteries are randomly selected and tested. What is the probability that both are defective, if the first one is not replaced after being tested
Found 2 solutions by katealdridge, stanbon:
Answer by katealdridge(100) About Me  (Show Source):
You can put this solution on YOUR website!
P(first event) = 3%2F30
P(second event) = 2%2F29
P(first then second w/o replacement) = %283%2F30%29+%2A+%282%2F29%29

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
In a box of thirty aaa batteries there are three defective batteries.
Two batteries are randomly selected and tested. What is the probability that both are defective,
Ans: 3C2/30C2 = 3/(15*29) = 1/145
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If the first one is not replaced after being tested
Ans: 3/30 * 2/29 = 6/(30*29) = 1/145
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Cheers,
Stan H.