  We perform a deductive study of accelerating Universe and focus on the
importance of variable time-dependent $\Lambda$ in the Einstein's field
equations under the phenomenological assumption, $\Lambda =\alpha H^2$ for the
full physical range of $\alpha$. The relevance of variable $\Lambda$ with
regard to various key issues like dark matter, dark energy, geometry of the
field, age of the Universe, deceleration parameter and barotropic equation of
state has been trivially addressed. The deceleration parameter and the
barotropic equation of state parameter obey a straight line relationship for a
flat Universe described by Friedmann and Raychaudhuri equations. Both the
parameters are found identical for $\alpha = 1$.
