15 * 4 = 60
13 * 6 = 78
17 * 2 = 34
21 * 3 = 63
11 * 8 = 88
14 * 7 = 98
Вычисления:
15 * 4 = (10 + 5) * 4 = 60
1) 10 * 4 = 40
2) 5 * 4 = 20
3) 40 + 20 = 60
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}40\\ 20\end{array}}\\ \begin{array}{r}60\end{array}\end{array}$
13 * 6 = (3 + 10) * 6 = 78
1) 3 * 6 = 18
2) 10 * 6 = 60
3) 18 + 60 = 78
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}18\\ 60\end{array}}\\ \begin{array}{r}78\end{array}\end{array}$
17 * 2 = (7 + 10) * 2 = 34
1) 7 * 2 = 14
2) 10 * 2 = 20
3) 14 + 20 = 34
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}14\\ 20\end{array}}\\ \begin{array}{r}34\end{array}\end{array}$
21 * 3 = (1 + 20) * 3 = 63
1) 1 * 3 = 3
2) 20 * 3 = 60
3) 3 + 60 = 63
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}3\\ 60\end{array}}\\ \begin{array}{r}63\end{array}\end{array}$
11 * 8 = (10 + 1) * 8 = 88
1) 10 * 8 = 80
2) 1 * 8 = 8
3) 80 + 8 = 88
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}80\\ 8\end{array}}\\ \begin{array}{r}88\end{array}\end{array}$
14 * 7 = (10 + 4) * 7 = 98
1) 10 * 7 = 70
2) 4 * 7 = 28
3) 70 + 28 = 98
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}70\\ 28\end{array}}\\ \begin{array}{r}98\end{array}\end{array}$