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1. \(31 + 30 = \ldots\)
2. \(29 + 40 = \ldots\)
3. \(80 + 15 = \ldots\)
4. \(44 + 50 = \ldots\)
5. \(78 + 20 = \ldots\)
6. \(33 + 30 = \ldots\)
7. \(40 + 31 = \ldots\)
8. \(36 + 50 = \ldots\)
9. \(15 + 40 = \ldots\)
10. \(27 + 70 = \ldots\)
11. \(40 + 59 = \ldots\)
12. \(40 + 58 = \ldots\)

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Verbetersleutel

1. \(\begin{align} & 31 + 30 \\ = & 30 + 31 \\= & 30 + \color{green}{30} + \color{red}{1} \\ = & \color{green}{60} + \color{red}{1} \\ = & \color{red}{61} \end{align}\)
2. \(\begin{align} & 29 + 40 \\ = & 40 + 29 \\= & 40 + \color{green}{20} + \color{red}{9} \\ = & \color{green}{60} + \color{red}{9} \\ = & \color{red}{69} \end{align}\)
3. \(\begin{align} & 80 + 15 \\= & 80 + \color{green}{10} + \color{red}{5} \\ = & \color{green}{90} + \color{red}{5} \\ = & \color{red}{95} \end{align}\)
4. \(\begin{align} & 44 + 50 \\ = & 50 + 44 \\= & 50 + \color{green}{40} + \color{red}{4} \\ = & \color{green}{90} + \color{red}{4} \\ = & \color{red}{94} \end{align}\)
5. \(\begin{align} & 78 + 20 \\ = & 20 + 78 \\= & 20 + \color{green}{70} + \color{red}{8} \\ = & \color{green}{90} + \color{red}{8} \\ = & \color{red}{98} \end{align}\)
6. \(\begin{align} & 33 + 30 \\ = & 30 + 33 \\= & 30 + \color{green}{30} + \color{red}{3} \\ = & \color{green}{60} + \color{red}{3} \\ = & \color{red}{63} \end{align}\)
7. \(\begin{align} & 40 + 31 \\= & 40 + \color{green}{30} + \color{red}{1} \\ = & \color{green}{70} + \color{red}{1} \\ = & \color{red}{71} \end{align}\)
8. \(\begin{align} & 36 + 50 \\ = & 50 + 36 \\= & 50 + \color{green}{30} + \color{red}{6} \\ = & \color{green}{80} + \color{red}{6} \\ = & \color{red}{86} \end{align}\)
9. \(\begin{align} & 15 + 40 \\ = & 40 + 15 \\= & 40 + \color{green}{10} + \color{red}{5} \\ = & \color{green}{50} + \color{red}{5} \\ = & \color{red}{55} \end{align}\)
10. \(\begin{align} & 27 + 70 \\ = & 70 + 27 \\= & 70 + \color{green}{20} + \color{red}{7} \\ = & \color{green}{90} + \color{red}{7} \\ = & \color{red}{97} \end{align}\)
11. \(\begin{align} & 40 + 59 \\= & 40 + \color{green}{50} + \color{red}{9} \\ = & \color{green}{90} + \color{red}{9} \\ = & \color{red}{99} \end{align}\)
12. \(\begin{align} & 40 + 58 \\= & 40 + \color{green}{50} + \color{red}{8} \\ = & \color{green}{90} + \color{red}{8} \\ = & \color{red}{98} \end{align}\)