$ABCD$ is a rhombus. If $AC = 16 \, cm$ and $BD = 30 \, cm$,then find the area of $ABCD$ in $cm^2$.

Prove that the sum of angles of any convex quadrilateral is $360^{\circ} .$

The diagonals $AC$ and $BD$ of a parallelogram $ABCD$ intersect each other at the point $O.$ If $\angle DAC = 32^{\circ}$ and $\angle AOB = 70^{\circ},$ then $\angle DBC$ is equal to: (in $^{\circ}$)

$A$ rectangular plot is given for constructing a house, having a measurement of $40 \, m$ long and $15 \, m$ in the front. According to the laws, a minimum of $3 \, m$ wide space should be left in the front and back each, and $2 \, m$ wide space on each of the other sides. Find the largest area where the house can be constructed (in $m^2$).

For a rhombus plot,its perimeter is $680 \, m$ and one of its diagonals is $300 \, m$. Find the area of the plot. (in $, m^2$)

State whether each of the following statements is true or false:
$(1)$ $ABCD$ is a rhombus. If $AB = 12 \, \text{cm}$, then the perimeter of $ABCD$ is $48 \, \text{cm}$.
$(2)$ $PQRS$ is a square. If $PR = 8 \, \text{cm}$, then the perimeter of $PQRS$ is $32 \, \text{cm}$.