Probably not that many compared to the other kinds of dinosaurs if they followed the usual rules about numbers for predators vs prey animals.
The big question about how tyranosaurs lived is how they would have hunted without having useful forelimbs. In today's world, hunters with teeth and claws (cats) can take on large prey singlehandedly while predators with just teeth (wolves and dogs) generally hunt in packs. Picture a pack of tyranosaurs coming after you?
I believe that 'pack hunting' is dictated by the available prey (ie, Giganotosaurs appear to have lived in family groups, which makes sense when the prevalent herbivore was a Titanosaur - Argentinosaurus - which could grow to 10 times the size of the largest Giganotosaurus)...if the prey is smaller, solo hunting appears to be more common...with TRex its an open questions because without a doubt both ceratopsians and Hadrosaurines in the late cretaceous could get VERY big indeed, though the ration was a lot closed to 1:1....I guess we won't know for sure unless someone finds a pack of Rexes burried by a flash flood (which did in the two Giganotosaur groups that Dr. Coria found in Patagonia...)