\[\sqrt{9000} = \sqrt{900 \cdot 10} = 30\sqrt{10};\]
\[\sqrt{0,4} = \sqrt{0,1 \cdot 4} = 2\sqrt{0,1};\]
\[\sqrt{1\frac{7}{9}} = \sqrt{\frac{16}{9}} = \frac{4}{3}.\]
\[Ответ:\ \sqrt{1\frac{7}{9}}.\]