SOLUTION: A circuit to run a model railroad has eight switches. Two are defective. If a person selects two switches at random and tests them, find the probability that the second one is de

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Question 328036: A circuit to run a model railroad has eight switches. Two are defective. If a person selects two switches at random and tests them, find the probability that the second one is defective, given that the first one is defective.
Answer by solver91311(24713) About Me  (Show Source):
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If you know there are exactly two defective switches and you have already selected one of them of 8 total, then there is one left out of 7 remaining.

John