  We show that two ways of manipulation of quantum entanglement, namely,
entanglement-assisted local transformation [D. Jonathan and M. B. Plenio, Phys.
Rev. Lett. {\bf 83}, 3566 (1999)] and multiple-copy transformation [S.
Bandyopadhyay, V. Roychowdhury, and U. Sen, Phys. Rev. A {\bf 65}, 052315
(2002)], are equivalent in the sense that they can asymptotically simulate each
other's ability to implement a desired transformation from a given source state
to another given target state with the same optimal success probability. As a
consequence, this yields a feasible method to evaluate the optimal conversion
probability of an entanglement-assisted transformation.
