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AP EAMCET2012MathematicsProbability

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 need is

Options

  1. A1 3
  2. B1 6
  3. C1 2
  4. D1 4

Correct answer

A. 1 3

Step-by-step solution

Required probability =P( first two test either both are faulty or both are not faulty) =P (First two are faulty) +P (First two are not faulty) aligned & = 2 4 1 3 + 2 4 1 3 & = 4 12 = 1 3 aligned

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