2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/65691We discuss the problem to count, or, more modestly, to estimate the number f(m,n) of unimodular triangulations of the planar grid of size $m\times n$. Among other tools, we employ recursions that allow one to compute the (huge) number of triangulations for small m and rather large n by dynamic programming; we show that this computation can be done in polynomial time if m is fixed, and present computational results from our implementation of this approach. We also present new upper and lower bounds for large m and n, and we report about results obtained from a computer simulation of the random walk that is generated by flips.30 pages, to appear in: ``British Combinatorial Surveys'' (C. D. Wensley, ed.), Cambridge University Press, 2003. This is an updated version containing minor changes suggested by the refereeCombinatoricsMetric Geometry05AXX; 52B20text