2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67898We prove that any three-point genus zero Gromov-Witten invariant on a type A Grassmannian is equal to a classical intersection number on a two-step flag variety. We also give symplectic and orthogonal analogues of this result; in these cases the two-step flag variety is replaced by a sub-maximal isotropic Grassmannian. Our theorems are applied, in type A, to formulate a conjectural quantum Littlewood-Richardson rule, and in the other classical Lie types, to obtain new proofs of the main structure theorems for the quantum cohomology of Lagrangian and orthogonal Grassmannians.15 pages, LaTeX2e, to appear in J. Amer. Math. SocAlgebraic Geometry14N35 (Primary) 14M15, 14N15, 05E15 (Secondary)text