A coin is tossed 7 times. Then the probability that at least 4 consecutive heads appear is

Let H denote the head, T the tail and ∗ any of the head  or tail. Then, P(H)=1/2,P(T)=1/2 and P(∗)=1. For at least  four consecutive heads, we should have any of the following patterns:Since all the above cases are mutually exclusive, the probability of getting at least four consecutive heads (on adding) is1/16+3/32=5/32