Abstract : In this paper . we apply the stochastic dynamic programming to approximate the mean project completion time in dynamic Markov PERT networks. It is assumed that the activity durations are independent random variables with exponential distributions. but some social and economical problems influence the mean of activity durations. https://www.roneverhart.com/Brown-Paper-Luncheon-Napkin-Live-Joyfully-13-x-13-500-count-box/