The value of $(1-\sqrt{2})+(\sqrt{2}-\sqrt{3})+(\sqrt{3}-\sqrt{4})+\ldots+(\sqrt{15}-\sqrt{16})$ is

$\left\{7 \frac{1}{2} + \frac{1}{2} \div \frac{1}{2} \text{ of } \frac{1}{4} - \frac{2}{5} \times 2 \frac{1}{3} \div 1 \frac{7}{8} \text{ of } \left(1 \frac{2}{5} - 1 \frac{1}{3}\right)\right\} = ?$

$\frac{1}{\left(2 \frac{1}{3}\right)}+\frac{1}{\left(1 \frac{3}{4}\right)}$ is equal to

If $x \times y = (x + 2)^2 (y - 2)$,then $7 \times 5 = ?$

If $\frac{x}{y} = \frac{4}{5}$,then the value of $\left(\frac{4}{7} + \frac{2y - x}{2y + x}\right)$ is

What approximate value will come in place of the question mark $(?)$ in the given equation? (You are not expected to calculate the exact value)
$2775 \times \frac{160}{\sqrt{?}} = 5550$