  When we model black hole accretion sources such as active galactic nuclei and
black hole X-ray binaries as advection-dominated accretion flows (ADAFs), it is
neccesary to use the global solution to the equations rather than the simpler
self-similar solution, since the latter is inaccurate in the region near the
black hole where most of the radiation is emitted. However, technically, it is
a difficult task to calculate the global solution because of the transonic
nature of the flow, which makes it a two-point boundary value problem. In this
paper we propose a simplified approach for calculating the global ADAF
solution. We replace the radial momentum equation by a simple algebraic
relation between the angular velocity of the gas and the Keplerian angular
velocity, while keeping all other equations unchanged. It is then easy to solve
the differential energy equations to obtain an approximate global solution. By
adjusting the free parameters, we find that for almost any accretion rate and
for $\alpha=0.1-0.3$ we can get good simplified global solutions. The predicted
spectra from the approximate solutions are very close to the spectra obtained
from the true global solutions.
