$\sqrt{10} \times \sqrt{250} = ?$

$\sqrt{80} + 3\sqrt{245} - \sqrt{125} = ?$

In the following questions,two equations numbered $I$ and $II$ are given. You have to solve both the equations and give the answer.
$I$: $\sqrt{25 x^{2}} - 125 = 0$
$II$: $\sqrt{361} y + 95 = 0$

$8787 \div 343 \times \sqrt{50} = ?$

Find the smallest number,which,when added to $3579$ gives a perfect square.

$\frac{\sqrt{1296}}{?} = \frac{?}{2.25}$