The value of the discriminant of the quadratic equation $4x^{2} + 20x + 25 = 0$ is $\ldots \ldots \ldots \ldots .$

If $-3$ is a solution of $2x^{2} + 5x + k = 0$,then $k = \ldots$

If the discriminant of $x^{2}-10x+(2k-1)=0$ is $40$,then $k=$...............

Find whether the following equation has real roots. If real roots exist,find them.
$5x^{2}-2x-10=0$

$A$ two-digit number is such that the product of its digits is $6$. When $9$ is subtracted from the number,the resulting number is the number obtained by interchanging the digits. Find the original number.

In the centre of a rectangular lawn of dimensions $50\, m \times 40\, m$,a rectangular pond has to be constructed so that the area of the grass surrounding the pond would be $1184\, m^{2}$ [see $Fig.$]. Find the length and breadth of the pond. (in $m$)