5
9×6=54
99×96=9504
999×996=995004
9999×9996=99950004
99999×999969999500004
7
999999×999996=999995000004
9999999×9999996=99999950000004
9999999×9999996=(10000000-1)×9999996
=99999960000000-9999996
=99999950000004