Увеличь:
30 +10 = 40
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}30\\ 10\end{array}}\\ \begin{array}{r}40\end{array}\end{array}$
40 + 20 = 60
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}40\\ 20\end{array}}\\ \begin{array}{r}60\end{array}\end{array}$
50 + 30 = 80
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}50\\ 30\end{array}}\\ \begin{array}{r}80\end{array}\end{array}$
Уменьши:
70 − 50 = 20
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}70\\ 50\end{array}}\\ \begin{array}{r}20\end{array}\end{array}$
60 − 40 = 20
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}60\\ 40\end{array}}\\ \begin{array}{r}20\end{array}\end{array}$
50 − 30 = 20
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}50\\ 30\end{array}}\\ \begin{array}{r}20\end{array}\end{array}$
20 больше 19 на 1:
20 − 19 = 1
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}20\\ 19\end{array}}\\ \begin{array}{r}1\end{array}\end{array}$
30 больше 29 на 1:
30 − 29 = 1
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}30\\ 29\end{array}}\\ \begin{array}{r}1\end{array}\end{array}$
40 больше 39 на 1:
40 − 39 = 1
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}40\\ 39\end{array}}\\ \begin{array}{r}1\end{array}\end{array}$
45 больше 10 на 35:
45 − 10 = 35
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}45\\ 10\end{array}}\\ \begin{array}{r}35\end{array}\end{array}$
58 больше 10 на 48:
58 − 10 = 48
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}58\\ 10\end{array}}\\ \begin{array}{r}48\end{array}\end{array}$
95 больше 10 на 85:
95 − 10 = 85
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}95\\ 10\end{array}}\\ \begin{array}{r}85\end{array}\end{array}$