91. Найдите значение выражения: 1) √72⋅√2; 2) √360⋅√490; 3) √242/√2; 4) √40/√0.025.

1) $$ \sqrt{72} \cdot \sqrt{2} = \sqrt{72 \cdot 2} = \sqrt{144} = 12 $$

2) $$ \sqrt{360} \cdot \sqrt{490} = \sqrt{36 \cdot 10} \cdot \sqrt{49 \cdot 10} = 6 \sqrt{10} \cdot 7 \sqrt{10} = 42 \cdot 10 = 420 $$

3) $$ \frac{\sqrt{242}}{\sqrt{2}} = \sqrt{\frac{242}{2}} = \sqrt{121} = 11 $$

4) $$ \frac{\sqrt{40}}{\sqrt{0.025}} = \sqrt{\frac{40}{0.025}} = \sqrt{\frac{40000}{25}} = \sqrt{1600} = 40 $$