Răspuns :
[tex]\it m_g = \sqrt{20\cdot45} =\sqrt{900} =30[/tex]
[tex]\sqrt{900} =\sqrt{9\cdot100} = 3\cdot 10 =30[/tex]
[tex]\sqrt{900} =\sqrt{9\cdot100} = 3\cdot 10 =30[/tex]