Three stars are found to have been formed from a molecular cloud. how many high density fragments must have existed in the cloud prior to star formation?

The formation of stars can be traced from the fragmentation of giant clouds of gas and dust called molecular clouds into many clumps. The gases present in the molecular clouds are H, He, H2, OH-, etc have the capability to shield the molecules from ultraviolet radiation coming from several stars found in our galaxy. There are also traces of other elements as well like silicates and iron. After the process of fragmentation, what happens next is that these further divided into a pack of million more of clumps.  Coming from a single molecular cloud, about 10 - 1000 stars can be formed from it.