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1. \(20 + 19 = \ldots\)
2. \(42 + 30 = \ldots\)
3. \(20 + 48 = \ldots\)
4. \(60 + 21 = \ldots\)
5. \(27 + 40 = \ldots\)
6. \(59 + 20 = \ldots\)
7. \(43 + 40 = \ldots\)
8. \(45 + 50 = \ldots\)
9. \(14 + 50 = \ldots\)
10. \(10 + 76 = \ldots\)
11. \(33 + 30 = \ldots\)
12. \(19 + 40 = \ldots\)

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Verbetersleutel

1. \(\begin{align} & 20 + 19 \\= & 20 + \color{green}{10} + \color{red}{9} \\ = & \color{green}{30} + \color{red}{9} \\ = & \color{red}{39} \end{align}\)
2. \(\begin{align} & 42 + 30 \\ = & 30 + 42 \\= & 30 + \color{green}{40} + \color{red}{2} \\ = & \color{green}{70} + \color{red}{2} \\ = & \color{red}{72} \end{align}\)
3. \(\begin{align} & 20 + 48 \\= & 20 + \color{green}{40} + \color{red}{8} \\ = & \color{green}{60} + \color{red}{8} \\ = & \color{red}{68} \end{align}\)
4. \(\begin{align} & 60 + 21 \\= & 60 + \color{green}{20} + \color{red}{1} \\ = & \color{green}{80} + \color{red}{1} \\ = & \color{red}{81} \end{align}\)
5. \(\begin{align} & 27 + 40 \\ = & 40 + 27 \\= & 40 + \color{green}{20} + \color{red}{7} \\ = & \color{green}{60} + \color{red}{7} \\ = & \color{red}{67} \end{align}\)
6. \(\begin{align} & 59 + 20 \\ = & 20 + 59 \\= & 20 + \color{green}{50} + \color{red}{9} \\ = & \color{green}{70} + \color{red}{9} \\ = & \color{red}{79} \end{align}\)
7. \(\begin{align} & 43 + 40 \\ = & 40 + 43 \\= & 40 + \color{green}{40} + \color{red}{3} \\ = & \color{green}{80} + \color{red}{3} \\ = & \color{red}{83} \end{align}\)
8. \(\begin{align} & 45 + 50 \\ = & 50 + 45 \\= & 50 + \color{green}{40} + \color{red}{5} \\ = & \color{green}{90} + \color{red}{5} \\ = & \color{red}{95} \end{align}\)
9. \(\begin{align} & 14 + 50 \\ = & 50 + 14 \\= & 50 + \color{green}{10} + \color{red}{4} \\ = & \color{green}{60} + \color{red}{4} \\ = & \color{red}{64} \end{align}\)
10. \(\begin{align} & 10 + 76 \\= & 10 + \color{green}{70} + \color{red}{6} \\ = & \color{green}{80} + \color{red}{6} \\ = & \color{red}{86} \end{align}\)
11. \(\begin{align} & 33 + 30 \\ = & 30 + 33 \\= & 30 + \color{green}{30} + \color{red}{3} \\ = & \color{green}{60} + \color{red}{3} \\ = & \color{red}{63} \end{align}\)
12. \(\begin{align} & 19 + 40 \\ = & 40 + 19 \\= & 40 + \color{green}{10} + \color{red}{9} \\ = & \color{green}{50} + \color{red}{9} \\ = & \color{red}{59} \end{align}\)