When a coin is tossed, the probability of getting a Head is $p, 0 < p < 1$. Let $N$ be the random variable denoting the number of tosses till the first Head appears, including the toss where the Head appears. Assuming that successive tosses are independent, the expected value of $N$ is
Actually, this is Geometric distribution.Here N is Geometric r.v which represents no of tosses required for first head.
The expected value of a Geom r.v N = 1/P
P(Head) = p
E(N) = 1/p
X->YZ , Y->XZ , ...