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Question
Seven persons are to be seated in a row. The probability that two particular persons sit next to each other is ______.
Options
`1/3`
`1/6`
`2/7`
`1/2`
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Solution
Seven persons are to be seated in a row. The probability that two particular persons sit next to each other is `2/7`.
Explanation:
The two particular persons to be seated next each other then, they form one group.
Now the permutation of 6 persons = 6! × 2!
And Total number of permutations of 7 persons = 7!
∴ Required probability = `(6! xx 2!)/(7!)`
= `(6! xx 2)/(7 xx 6!)`
= `2/7`
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