The man will be one step away from the starting point, if (1). either he is one step ahead or (2).one step behind the starting point.
The man will be one step ahead at the end of eleven steps, if he moves six steps forward and five steps backwards. The probability of this event is 11C6 (0.4)6(0.6)5.
The man will be one step behind at the end of eleven steps. if he moves six steps backwards and five steps forward. The probability of this event is 11C6(0.6)6(0.4)5.
.'. Required probability = 11C6 (0.4)6(0.6)5 + 11C6(0.6)6(0.4)5
= 11C6(0.24)5
