If ten persons sit in a row, then the probability that three particular persons are always together is?
Choose one: A) 1/5 B) 1/4 C) 1/9 D) 1/6 E) 1/15
Ten persons can be arranged in a row in 10! ways.   Treat the three persons to sit together as one unit then there eight persons and they can be arranged in 8! ways.   Again three persons can be arranged among them selves in 3! ways.   Favourable outcomes = 3!8!   Required probability = 3!8!/10! = 1/15   Answer:1/15
<result>E</result>
If ten persons sit in a row, then the probability that three particular persons are always together is?