There are four machines and it is known that exactly two of them are faulty machines are identified. Then the probability that only two tests are needed

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Solution

The correct option is B $1 / 6$
The probability that only two tests are needed $=$ probability that the first machine tested is faulty $\times$ probability that the second machine tested is faulty $= \frac{2}{4} \times \frac{1}{3} = \frac{1}{6}$

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There are four machines and it is known that exactly two of them are faulty machines are identified. Then the probability that only two tests are needed

The correct option is B 1/6The probability that only two tests are needed = probability that the first machine tested is faulty × probability that the second machine tested is faulty =24×13=16

The correct option is B $1 / 6$
The probability that only two tests are needed $=$ probability that the first machine tested is faulty $\times$ probability that the second machine tested is faulty $= \frac{2}{4} \times \frac{1}{3} = \frac{1}{6}$