In order to find the answer for this, we need to use proportions and cross multiply. Given that 3/4 of bread crumbs yields 3 hamburgers, and he plans on using 1 and 1/3 cup of bread crumbs, it will look like this: 3/4 over 3 : 4/3 over ?. So we cross multiply 3 by 4/3 and we get 4. Then divide 4 by 3/4 and we get 16/3 or 5 and 1/3. Therefore, the pounds of burgers that he needs to use is 5 and 1/3 pounds. Hope this helps.