three students are to be seated in a row of 10 chairs. What is the probability that they will be seated in adjacent seats

Answer 1

There are 10! ways to place 10 students in 10 chairs in a row.
There are 8! ways to arrange a group of 3 students with 7 other students.
Among the three students (in a group), they can arrange themselves in 3! different ways.

So the probability that they will be seated together is
(8!3!)/10!