Ta có:

• $\sqrt{911,9}=\sqrt{9,119}.\sqrt{100}\approx 3,019,10\approx 30,19$
• $\sqrt{91190}=\sqrt{9,119}.\sqrt{10000}\approx 3,019.100\approx 301,9$
• $\sqrt{0,09119}=\sqrt{9,119}.\sqrt{0,01}\approx 3,019.0,1\approx 0,3019$
• $\sqrt{0,0009119}=\sqrt{9,119}.\sqrt{0,0001}\approx 3,019.0,01\approx 0,03019$