1. The problem statement, all variables and given/known data The number of ways in which 4 persons P1,P2,P3,P4 can be arranged in a row such that P2 does not follow P1, P3 does not follow P2 and P4 does not follow P3 is 3. The attempt at a solution Let us assume that P1 occupies the first position. So, the next position can be occupied by P3 or P4. Thus, there are 2 ways by which the required arrangement can be made, P1 occupying the first seat. Since there are 4 persons, we have 2*4=8 ways by which the persons can be seated according to the given condition. But this is not correct. I can't figure out where I'm going wrong.