$\sqrt{18\ast 200}=\sqrt{9\ast 2\ast 2\ast 100}=\sqrt{3^2\ast 2^2\ast {10}^2}=\sqrt{3^2}\ast \sqrt{2^2}\ast \sqrt{{10}^2}=3\ast 2\ast 10=60$

$\sqrt{3,6\ast 0,4}=\sqrt{36\ast 0,1\ast 0,1\ast 4}=\sqrt{6^2\ast 0,1^2\ast 2^2}=\sqrt{6^2}\ast \sqrt{0,1^2}\ast \sqrt{2^2}=6\ast 0,1\ast 2=1,2$

$\sqrt{14,4\ast 0,9}=\sqrt{144\ast 0,1\ast 0,1\ast 9}=\sqrt{{12}^2\ast 0,1^2\ast 3^2}=\sqrt{{12}^2}\ast \sqrt{0,1^2}\ast \sqrt{3^2}=12\ast 0,1\ast 3=3,6$

$\sqrt{13\ast 52}=\sqrt{13\ast 4\ast 13}=\sqrt{{13}^2\ast 2^2}=\sqrt{{13}^2}\ast \sqrt{2^2}=13\ast 2=26$

$\sqrt{12,5\ast 32}=\sqrt{12,5\ast 2\ast 16}=\sqrt{25\ast 16}=\sqrt{5^2\ast 4^2}=\sqrt{5^2}\ast \sqrt{4^2}=5\ast 4=20$

$\sqrt{108\ast 27}=\sqrt{36\ast 3\ast 3\ast 9}=\sqrt{6^2\ast 3^2\ast 3^2}=\sqrt{6^2}\ast \sqrt{3^2}\ast \sqrt{3^2}=6\ast 3\ast 3=54$