Mot dan vit troi dang bay thi gap mot con vit troi bay theo chieu nguoc lai,con vit troi nay cat tieng chao:''Chao 100 ban a''.Con vit troi dau dan lien dap:''Ban nham roi,chung toi khong phai 100,ma chung toi them chung toi ,them 1/2 chung toi,them 1/4 chung toi va them ban nua thi chung ta moi day 100''.Hoi dan vit troi do co bao nhieu con?