Question

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

(1) 1/3

(2) 1/6

(3) 1/2

(4) 1/4

Answer 1

Correct Option (2) 1/6

Explanation:

Since only two tests are needed, one faulty machine should be caught in the first test and the other one in the second test