  We study continuous time Markov processes on graphs. The notion of frequency
is introduced, which serves well as a scaling factor between any Markov time of
a continuous time Markov process and that of its jump chain. As an application,
we study ``multi-person simple random walks'' on a graph G with n vertices.
There are n persons distributed randomly at the vertices of G. In each step of
this discrete time Markov process, we randomly pick up a person and move it to
a random adjacent vertex. We give estimate on the expected number of steps for
these $n$ persons to meet all together at a specific vertex, given that they
are at different vertices at the begininng. For regular graphs, our estimate is
exact.
