  In order to account for the observed cosmic acceleration, a modification of
the ansatz for the variation of density in Friedman-Robertson-Walker (FRW)
models given by Islam is proposed. The modified ansatz leads to an equation of
state which corresponds to that of a variable Chaplygin gas, which in the
course of evolution reduces to that of a modified generalized Chaplygin gas
(MGCG) and a Chaplygin gas (CG), exhibiting late-time acceleration.
