As 0.4+0.6=1, the man either takes a step forward or a step backward. Let a step forward be a success and a step backward be a failure. Then, the probability of success in one stepp=0.4=
2
5
The probability of failure in one step=q=0.6=
3
5
In 11 steps he will be one step away from the starting point if the numbers of successes and failures differ by 1. So, the number of successes=6 The number of failures=5 or the number of successes =5 The number of failures =6 ∴ the required probability =11C6p6q5+11C5p5q6