[tex]2:1=\dfrac{2}{1}=\dfrac{2\cdot2}{1\cdot2}=\dfrac{4}{2}=4:2\\\\2:1=\dfrac{2}{1}=\dfrac{2\cdot3}{1\cdot3}=\dfrac{6}{3}=6:3\\\\2:1=\dfrac{2}{1}=\dfrac{2\cdot4}{1\cdot4}=\dfrac{8}{4}=8:2\\\\2:1=\dfrac{2}{1}=\dfrac{2\cdot10}{1\cdot10}=\dfrac{20}{10}=20:10[/tex]
