Aby zamienić ułamek zwykły na dziesiętny, możemy podzielić jego licznik przez mianownik.

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a)

$\frac{3}{5}=0,6$  

$\begin{array}{l}\underline{0,6}\\ 3:5\\ \underline{-0}\\ 30\\ \underline{-30}\\ =\end{array}$

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$\frac{17}{20}=0,85$  

$\begin{array}{l}\underline{0,85}\\ 17:20\\ \underline{-0}\\ 170\\ \underline{-160}\\ 100\\ \underline{-100}\\ =\end{array}$

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$\frac{3}{8}=0,375$  

$\begin{array}{l}\underline{0,375}\\ 3:8\\ \underline{-0}\\ 30\\ \underline{-24}\\ 60\\ \underline{-56}\\ 40\\ \underline{-40}\\ =\end{array}$

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$\frac{21}{25}=0,84$  

$\begin{array}{l}\underline{0,84}\\ 21:25\\ \underline{-0}\\ 210\\ \underline{-200}\\ 100\\ \underline{-100}\\ =\end{array}$

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$\frac{3}{4}=0,75$  

$\begin{array}{l}\underline{0,75}\\ 3:4\\ \underline{-0}\\ 30\\ \underline{-28}\\ 20\\ \underline{-20}\\ =\end{array}$

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b)

$2\frac{7}{8}=\frac{2\cdot 8+7}{8}=\frac{16+7}{8}=\frac{23}{8}=2,875$   

$\begin{array}{l}\underline{2,875}\\ 23:8\\ \underline{-16}\\ 70\\ \underline{-64}\\ 60\\ \underline{-56}\\ 40\\ \underline{-40}\\ =\end{array}$

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$1\frac{53}{80}=\frac{1\cdot 80+53}{80}=\frac{133}{80}=1,6625$    

$\begin{array}{l}\underline{1,6625}\\ 133:80\\ \underline{-80}\\ 530\\ \underline{-480}\\ 500\\ \underline{-480}\\ 200\\ \underline{-160}\\ 400\\ \underline{-400}\\ =\end{array}$

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$1\frac{41}{50}=\frac{41+50}{50}=\frac{91}{50}=1,82$   

$\begin{array}{l}\underline{1,82}\\ 91:50\\ \underline{-50}\\ 410\\ \underline{-400}\\ 100\\ \underline{-100}\\ =\end{array}$

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$2\frac{15}{16}=\frac{2\cdot 16+15}{16}=\frac{47}{16}=2,9375$   

$\begin{array}{l}\underline{2,9375}\\ 47:16\\ \underline{-32}\\ 150\\ \underline{-144}\\ 60\\ \underline{-48}\\ 120\\ \underline{-112}\\ 80\\ \underline{-80}\\ =\end{array}$

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$2\frac{74}{125}=\frac{2\cdot 125+74}{125}=\frac{324}{125}=2,592$  

$\begin{array}{l}\underline{2,592}\\ 324:125\\ \underline{-250}\\ 740\\ \underline{-625}\\ 1150\\ \underline{-1125}\\ 250\\ \underline{-250}\\ =\end{array}$