Решение:
- \(\sqrt{81 \cdot 900} = \sqrt{81} \cdot \sqrt{900} = 9 \cdot 30 = 270\)
- \(\sqrt{0,36 \cdot 49} = \sqrt{0,36} \cdot \sqrt{49} = 0,6 \cdot 7 = 4,2\)
- \(\sqrt{12 \frac{1}{4}} = \sqrt{\frac{49}{4}} = \frac{\sqrt{49}}{\sqrt{4}} = \frac{7}{2} = 3,5\)
- \(\sqrt{10 \frac{9}{16}} = \sqrt{\frac{169}{16}} = \frac{\sqrt{169}}{\sqrt{16}} = \frac{13}{4} = 3,25\)
Ответ: а) 270; б) 4,2; в) 3,5; г) 3,25.