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Study Stuff for MCA Examinations - NIMCET
Study Stuff for MCA Examinations - NIMCET
Previous Year Question (PYQs)
Three letters are dictated to three persons and an envelope is addressed to each of them.
The letters are inserted into the envelopes at random so that each envelope contains exactly one letter.
What is the probability that at least one letter is in its proper envelope?
Solution
Total permutations of 3 letters = $3! = 6$. Derangements (no letter in correct envelope) = $!3 = 2$. Hence, number of favorable cases (at least one correct) = $6 - 2 = 4$. Probability $= \dfrac{4}{6} = \dfrac{2}{3}$.Online Test Series, Information About Examination,
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