Find the area of a triangle whose sides are $13\, cm$,$14\, cm$,and $15\, cm$. (in $, cm^2$)

Sanya has a piece of land which is in the shape of a rhombus (see figure). She wants her one daughter and one son to work on the land and produce different crops. She divided the land into two equal parts. If the perimeter of the land is $400\, m$ and one of the diagonals is $160\, m$,how much area will each of them get for their crops (in $, m^2$)?

There is a triangular party plot with side lengths of $200\,m$,$210\,m$,and $290\,m$. Calculate the cost of raising a lawn in that plot at the rate of Rs. $5/m^2$.

Sides of a triangle are in the ratio of $12 : 17 : 25$ and its perimeter is $540 \, cm$. Find its area.

Find the area of a triangle two sides of which are $18 \, cm$ and $10 \, cm$ and the perimeter is $42 \, cm$.

For a plank in the shape of a parallelogram,the adjacent sides measure $12 \, cm$ and $17 \, cm$,and one of its diagonals measures $25 \, cm$. Find the cost of painting the plank at the rate of Rs. $3$ per $cm^2$.