If $3 \sqrt{5}+\sqrt{125}=17.88$,then what will be the value of $\sqrt{80}+6 \sqrt{5}$?

$A$ General wishing to draw up his $5180$ men in the form of a solid square found that he had $4$ men less. If he could get four more men and form the solid square,the number of men in the front row is

In the following questions,two equations numbered $I$ and $II$ are given. You have to solve both the equations and give the answer.
$I$: $\frac{5}{7} - \frac{5}{21} = \frac{\sqrt{x}}{42}$
$II$: $\frac{\sqrt{y}}{4} + \frac{\sqrt{y}}{16} = \frac{250}{\sqrt{y}}$

$\sqrt{0.00004761} = ?$

Find the least number,which,when multiplied with $74088$ will make it a perfect square.

The least perfect square,which is divisible by $21, 36$ and $66$ completely is