2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83675We reconsider the valuation of barrier options by means of binomial trees from a "forward looking" prospective rather than the more conventional "backward induction" one used by standard approaches. This reformulation allows us to write closed-form expressions for the value of European and American put barrier-options on a non-dividend-paying stock.12 pages, 1 figureGeneral PhysicsCondensed Mattertext