Вычислите: а) \(3\sqrt{0,16}-0,1\sqrt{225}\); б) \(0,2\sqrt{900}+1,8\sqrt{\frac{1}{9}}\); в) \(0,3\sqrt{1,21}\cdot\sqrt{400}\); г) \(5:\sqrt{0,25}\cdot\sqrt{0,81}\).

1. \(3\sqrt{0.16}-0.1\sqrt{225}=3\cdot0.4-0.1\cdot15=1.2-1.5=-0.3\).
2. \(0.2\sqrt{900}+1.8\sqrt{\frac{1}{9}}=0.2\cdot30+1.8\cdot\frac{1}{3}=6+0.6=6.6\).
3. \(0.3\sqrt{1.21}\cdot\sqrt{400}=0.3\cdot1.1\cdot20=6.6\).
4. \(5:\sqrt{0.25}\cdot\sqrt{0.81}=5:0.5\cdot0.9=10\cdot0.9=9\).

Ответ: а) \(-0.3\); б) \(6.6\); в) \(6.6\); г) \(9\).