Question

If 12 persons are seated in a row, the number of ways of selecting 3 persons from them, so that no two of them are seated next to each other is

 (a) 85 (b) 100 (c) 120 (d) 240 (e) None of these

Answer 1

(c) The number of ways of selecting 3 persons from 12 people under the given conditon :
Number of ways of arranging 3 people among 9 people seated in a row, so that no two of them are consecutive
= Number of ways of choosing 3 places out of the 10
[8 in between and 2 extremes]