Cách 1:
a) 4 + 5 = 9 b) 30 + 10 = 40 c) 52 + 41 + 6 = 99
Cách 2: Đặt tính rồi tính
\(\begin{array}{*{20}{c}}{a)\,\,}\\{}\\{}\end{array}\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}4\\5\end{array}}\\\hline{\,\,\,\,9}\end{array}\) \(\begin{array}{*{20}{c}}{b)\,\,}\\{}\\{}\end{array}\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{30}\\{10}\end{array}}\\\hline{\,\,\,\,40}\end{array}\) \(\begin{array}{*{20}{c}}{c)}\\{}\\{}\\{}\end{array}\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{52}\\{41}\\{\,\,\,6}\end{array}}\\\hline{\,\,\,\,99}\end{array}\)
