2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/70800We show that the left-greedy algorithm is a better algorithm than the right-greedy algorithm for sorting permutations using t stacks in series when t>1. We also supply a method for constructing some permutations that can be sorted by t stacks in series and from this get a lower bound on the number of permutations of length n that are sortable by t stacks in series. Finally we show that the left-greedy algorithm is neither optimal nor defines a closed class of permutations for t>2.9 pages, 7 figures, To be published in Annals of Combinatorics. The new version makes a few grammatical changes, clarifies a definition, and fixes the figuresCombinatorics05A05 (primary), 68R05, 68W01 (secondary)text