6 persons A, B, C, D, E and F are sitting in a row facing north (not necessarily in the same order). A is the immediate neighbour of D and F. F is the immediate neighbour of E and A. B is in the second position from the right end. If D is not at any of the ends, then how many persons are sitting towards the left of D?

3

Answer: 3

In this question we will first place B second from the right end.

There will be now two ways to place the others

E   F  A  D  or  D  A  F  E, but we know D cannot sit at corner so now only one option is left. And C sits at the right end