Giải thích các bước giải:

Ta co:

$\overline{abcdeg}$

$=\overline{abc}\cdot 1000+\overline{deg}$

$=\overline{abc}\cdot 1001-\overline{abc}+\overline{deg}$

$=\overline{abc}\cdot 91\cdot 11-(\overline{abc}-\overline{deg})$

Mà $(\overline{abc}-\overline{deg})\quad\vdots\quad 11$

$\to \overline{abc}\cdot 91\cdot 11-(\overline{abc}-\overline{deg})\quad\vdots\quad 11$

$\to \overline{abcdeg}\quad\vdots\quad 11$