Probability 3 Question 13
13. There are four machines and it is known that exactly two of them are faulty. They are tested, one by one, in a random order till both the faulty machines are identified. Then, the probability that only two tests are needed, is
(a)
(b)
(c)
(d)
(1998, 2M)
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Solution:
- Probability that only two tests are needed =Probability that the first machine tested is faulty
