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

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) (Show Source): You can put this solution on YOUR website!

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

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