SOLUTION: A batch of pills consist of 9 good pills and 3 that are defective (contain the wrong amount of the drug). If 4 pills are randomly selected without replacement, what is the probabil

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Question 1183656: A batch of pills consist of 9 good pills and 3 that are defective (contain the wrong amount of the drug). If 4 pills are randomly selected without replacement, what is the probability that all 3 of the defective pills are selected?
Found 2 solutions by VFBundy, ikleyn:
Answer by VFBundy(438)   (Show Source): You can put this solution on YOUR website!


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Answer by ikleyn(52905)   (Show Source): You can put this solution on YOUR website!
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A batch of pills consist of 9 good pills and 3 that are defective (contain the wrong amount of the drug).
If 4 pills are randomly selected without replacement, what is the probability
that all 3 of the defective pills are selected?
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We should calculate the number of the quadruples that contain 3 defective pills and 1 good pill.


Then we should relate this number to the number of all possible quadruples of 9+3 = 12 pills.


The numerator of the fraction is   = 1*9 = 9.


The denominator of the fraction is   =  = 495.


The final probability under the problem's question is   =  = 0.01818 = 1.818%  (rounded).    ANSWER

Solved.



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