Fuzzy inventory model for deteriorating items with permissible delay in payment

In this paper, we extend Jamal et al. [A.M.M. Jamal, B.R. Sarker, S. Wang, An ordering policy for deteriorating items with allowable shortage and permissible delay in payment, Journal of Operations Research Society 48 (1997) 826–833.] model by fuzzifying the carrying cost rate, interest paid rate and interest earned rate simultaneously, based on the interval-valued fuzzy numbers and triangular fuzzy number to fit the real world. We then prove that the estimate of total variable cost per unit time in the fuzzy sense is a strictly pseudo-convex function. As a result, there exists a unique optimal solution to our proposed model. Moreover, we apply the Jamal et al. example to show the results and to compare with the Jamal et al. model.