Well.. wait a minute. If you mean, "How many seeds does it take to get a HARVESTABLE (read: female) plant, that answer is cloudy. You could plant 8 seeds and get 8 males, none smokeable. You could get 8 females. You could get 3/3/2 male/female/hermaphrodite.. and on and on and on. Plant your 5 seeds, put into flowering, see which are females.
More importantly, read this site for a while before you ask questions. Just follow a couple of grow journals and see what happens. Here.. look in my signature.. read mine. It has the answers you seek.