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Grade 12th passAlgebra

There are four calculators and it is known that exactly two of them were defective. They Are tested one by one, in a random order till both the defective calculators are identified. Then the probability that only two tests are required is ____

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Profile image of Teja Sadgun
8 Years agoGrade 12th pass
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1 Answer

Profile image of Arun
8 Years ago
there are 2 ways of getting the machines in the first 2 tries. First possibility, you get both faulty, or you get both correct(since, then you know the left ones are faulty). Thus solving both possibilities: (2/4)x (1/3) x 2 since both have same chances
Hence when solving,
We get answer as  1/3