Seven different teachers are to deliver lectures in seven periods of a class on a particular day. A,B and C are three of the teachers. The no.of ways in which a routine for the day can be made such that A delivers his lacture before B and B before C is ___
(a) 420
(b) 120
(c) 210
(d) none of these
Correct option: (d) none of these
Explanation:
The order of a, b, c is not changing
Number of arrangement by keeping order of a,b,c as given = 7!/3! = 7 x 6 x 5 x 4 = 840
