24 * 5:
1 способ:
24 * 5 = (10 + 8 + 6) * 5 = 120
1) 10 * 5 = 50
2) 8 * 5 = 40
3) 6 * 5 = 30
4) 50 + 40 + 30 = 120
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}50\\ 40\end{array}}\\ \begin{array}{r}90\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}90\\ 30\end{array}}\\ \begin{array}{r}120\end{array}\end{array}$
2 способ:
24 * 5 = (8 + 8 + 8) * 5 = 120
1) 8 * 5 = 40
2) 8 * 5 = 40
3) 8 * 5 = 40
4) 40 + 40 + 40 = 120
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}40\\ 40\end{array}}\\ \begin{array}{r}80\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}80\\ 40\end{array}}\\ \begin{array}{r}120\end{array}\end{array}$
140 * 6:
1 способ:
140 * 6 = (100 + 20 + 20) * 6 = 840
1) 100 * 6 = 600
2) 20 * 6 = 120
3) 20 * 6 = 120
4) 600 + 120 + 120 = 840
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}600\\ 120\end{array}}\\ \begin{array}{r}720\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}720\\ 120\end{array}}\\ \begin{array}{r}840\end{array}\end{array}$
2 способ:
140 * 6 = (80 + 40 + 20) * 6 = 840
1) 80 * 6 = 480
2) 40 * 6 = 240
3) 20 * 6 = 120
4) 480 + 240 + 120 = 840
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}480\\ 240\end{array}}\\ \begin{array}{r}720\end{array}\end{array}$
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}720\\ 120\end{array}}\\ \begin{array}{r}840\end{array}\end{array}$