  We derive a simple analytical solution for the evolution of a close binary
with nuclear time-scale driven mass transfer from a giant. This solution is
based on the well-known fact that the luminosity and the radius of a giant
scale to a good approximation as simple power laws of the mass M_c of the
degenerate helium core. Comparison with results of numerical calculations by
Webbink, Rappaport & Savonije (1983) show the analytical solution and the power
law approximation to be quite accurate. The analytical solution presented does
also allow (in parametrized form) for non-conservative mass transfer.
Furthermore it is shown that the near constancy of the mass transfer rate over
most of the mass transfer phase seen in the results by Webbink, Rappaport &
Savonije is not a generic feature of this type of evolution but rather a
consequence of a particular choice of parameters. The analytical solution also
demonstrates that the level of mass transfer is largely set by the core mass of
the giant at the onset of mass transfer. Finally we show that the model is
selfconsistent and discuss its applicability to low-mass X-ray binaries.
