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}


29+29型のタイル操作

\begin{array}{rr} & 47 \\ + & 26 \\ \hline \end{array}の場合

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  1. 一の位・・・7こ+6こ=13こ
  2. 10こは、1本だから十の位にくり上げる
  3. 1の位にのこった3を書く
  4. 十の位・・・4本+2本=6本
  5. くり上がった1本を合わせて7本
  6. 7本と3こで、こたえは73