a)

b) Ta có:  10 \(l\) + 3 \(l\) + 3 \(l\) + 2 \(l\) + 2 \(l\) + 2 \(l\) = 22 \(l\).

Vậy ta có kết quả như sau:

Học sinh đặt đồ vật lên đĩa cân, sau đó đọc số đo trên cân đồng hồ.

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{12}\\{48}\end{array}}\\\hline{\,\,\,60}\end{array}\)                                      \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{59}\\{21}\end{array}}\\\hline{\,\,\,80}\end{array}\)

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{74}\\{\,\,6}\end{array}}\\\hline{\,\,\,\,80}\end{array}\)                                      \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{85}\\{\,\,5}\end{array}}\\\hline{\,\,\,90}\end{array}\)

\(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{63}\\{38}\end{array}}\\\hline{\,\,\,25}\end{array}\)                                      \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{70}\\{26}\end{array}}\\\hline{\,\,\,44}\end{array}\)

\(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{54}\\{\,\,9}\end{array}}\\\hline{\,\,\,45}\end{array}\)                                      \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{30}\\{\,\,\,5}\end{array}}\\\hline{\,\,\,\,25}\end{array}\)

\(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{31}\\{18}\end{array}}\\\hline{\,\,\,13}\end{array}\)                       \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{95}\\{38}\end{array}}\\\hline{\,\,\,\,57}\end{array}\)                       \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{45}\\{16}\end{array}}\\\hline{\,\,\,29}\end{array}\)