\[\boxed{\mathbf{893\ (893).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \sqrt{108} \cdot \sqrt{3} = \sqrt{36 \cdot 3 \cdot 3} = 18\]
\[2)\ \sqrt{52} \cdot \sqrt{13} = \sqrt{4 \cdot 13 \cdot 13} =\]
\[= 2 \cdot 13 = 26\]
\[3)\ \sqrt{160} \cdot \sqrt{250} =\]
\[= \sqrt{16 \cdot 10 \cdot 10 \cdot 25} =\]
\[= 4 \cdot 10 \cdot 5 = 200\]
\[4)\ \sqrt{0,4} \cdot \sqrt{4,9} =\]
\[= \sqrt{4 \cdot 0,1 \cdot 0,1 \cdot 49} =\]
\[= 2 \cdot 0,1 \cdot 7 = 1,4\]
\[5)\frac{\sqrt{258}}{\sqrt{2}} = \sqrt{\frac{288}{2}} = \sqrt{144} = 12\]
\[6)\frac{\sqrt{90}}{\sqrt{0,225}} = \sqrt{\frac{90}{225 \cdot 0,001}} =\]
\[= \sqrt{\frac{90000}{225}} = \frac{300}{15} = 20\ \]