Вычислите: 1) √16 · √49; 2) √0,81 · √36; 3) √(9/64); 4) √(81/49).

1. \(\sqrt{16}\cdot\sqrt{49}=4\cdot7=28\).
2. \(\sqrt{0.81}\cdot\sqrt{36}=0.9\cdot6=5.4\).
3. \(\sqrt{\frac{9}{64}}=\frac{\sqrt{9}}{\sqrt{64}}=\frac{3}{8}\).
4. \(\sqrt{\frac{81}{49}}=\frac{\sqrt{81}}{\sqrt{49}}=\frac{9}{7}\).

Ответ: 1) 28; 2) 5,4; 3) \(\frac{3}{8}\); 4) \(\frac{9}{7}\).