Đặt tính rồi tính. 312 × 3                    105 × 7                    81 × 9

Lời giải

\[\begin{array}{l}\underline { \times \begin{array}{*{20}{c}}{312}\\{\,\,\,\,\,3}\end{array}} \\\,\,\,936\end{array}\]     \[\begin{array}{l}\underline { \times \begin{array}{*{20}{c}}{105}\\{\,\,\,\,\,\,7}\end{array}} \\\,\,\,\,735\end{array}\]   \[\begin{array}{l}\underline { \times \begin{array}{*{20}{c}}{81}\\{\,\,\,9}\end{array}} \\\,729\end{array}\]