2位数のたし算

水道方式で初めて学ぶ複合過程が２位数のたし算です。

2-9分類法による指導順序

※水源地は３位数の加法にあるため、２位数同士の最も典型的な型は「小水源地」と名づけられました。

［小水源地］ $\begin{array}{rr} & 22 \\ + & 22 \\ \hline \end{array}$	$\begin{array}{rr} & 22 \\ + & 20 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 20 \\ + & 22 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 20 \\ + & 20 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 22 \\ + & 2 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 2 \\ + & 22 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 20 \\ + & 2 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 2 \\ + & 20 \\ \hline \end{array}$
［くり上がり１回］ $\begin{array}{rr} & 29 \\ + & 29 \\ \hline \end{array}$	$\begin{array}{rr} & 29 \\ + & 21 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 29 \\ + & 9 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 9 \\ + & 29 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 29 \\ + & 1 \\ \hline \end{array}$ ↓ $\begin{array}{rr} & 1 \\ + & 29 \\ \hline \end{array}$

［小水源地］
$\begin{array}{rr} & 22 \\ + & 22 \\ \hline \end{array}$

$\begin{array}{rr} & 22 \\ + & 20 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 20 \\ + & 22 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 20 \\ + & 20 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 22 \\ + & 2 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 2 \\ + & 22 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 20 \\ + & 2 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 2 \\ + & 20 \\ \hline \end{array}$

［くり上がり１回］
$\begin{array}{rr} & 29 \\ + & 29 \\ \hline \end{array}$

$\begin{array}{rr} & 29 \\ + & 21 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 29 \\ + & 9 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 9 \\ + & 29 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 29 \\ + & 1 \\ \hline \end{array}$
↓
$\begin{array}{rr} & 1 \\ + & 29 \\ \hline \end{array}$