Dynamical Age vs Spectral Age of the Lobes of Selected Giant Radio
  Sources (GRSs)
  Dynamical ages of the opposite lobes determined {\sl independently} of each
other suggest that their ratios are between $\sim$1.1 to $\sim$1.4. Demanding
similar values of the jet power and the radio core density for the same GRS, we
look for a {\sl self-consistent} solution for the opposite lobes, which results
in different density profiles along them found by the fit. A comparison of the
dynamical and spectral ages shows that their ratio is between $\sim$1 and
$\sim$5, i.e. is similar to that found for smaller radio galaxies. Two causes
of this effect are pointed out.
