Find the area of a triangle,two sides of which are $15\,cm$ and $28\,cm$ and the perimeter is $84\,cm$. (in $,cm^2$)

Area of a square $= \frac{(\ldots \ldots . .)^{2}}{2} .$

The sides of $\Delta PQR$ measure $13 \, cm$, $14 \, cm$, and $15 \, cm$. Find its area in $cm^2$.

Find the cost of laying grass in a triangular field of sides $50 \, m$,$65 \, m$,and $65 \, m$ at the rate of $Rs \, 7$ per $m^2$ (in $Rs$).

Calculate the area of the shaded region in the figure.

The triangular side walls of a flyover have been used for advertisements. The sides of the walls are $13 \, m$,$14 \, m$,and $15 \, m$. The advertisements yield an earning of $Rs \, 2000$ per $m^2$ a year. $A$ company hired one of its walls for $6$ months. How much rent did it pay? (in $Rs$)