Hej!
[tex]0,3\cdot0,1=\frac{3}{10}\cdot\frac{1}{10}=\frac{3\cdot1}{10\cdot10}=\frac{3}{100}\\\\0,13\cdot0,2=\frac{13}{100}\cdot\frac{2}{10}=\frac{13\cdot2}{100\cdot10}=\frac{26}{1000}=\frac{13}{500}\\\\1,1\cdot0,07=1\frac{1}{10}\cdot\frac{7}{100}=\frac{11}{10}\cdot\frac{7}{100}=\frac{11\cdot7}{10\cdot1000}=\frac{77}{1000}\\\\0,91\cdot0,001=\frac{91}{100}\cdot\frac{1}{1000}=\frac{91\cdot1}{100\cdot1000}=\frac{91}{100000}[/tex]
