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`

Answer 1

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`