The sides of a triangular field are $320 \mathrm{m}$, $200 \mathrm{m}$ and $180 \mathrm{m}$ long. Using ruler and compasses only, draw the plan of the field using the scale $50 \mathrm{m}=1 \mathrm{cm}$. Construct the altitude of the triangle on the side representing $320 \mathrm{m}$. If the area of the actual field can be calculated by measuring its altitude as $k {\mathrm{m}}^2$, then find the value of $k$.

If the area of the equilateral triangle whose side is $12 \mathrm{cm}$ is $k \mathrm{cm}$ then find $k$ upto three decimal places.

If the area of the equilateral triangle whose side is $5 \mathrm{cm}$ is $k {\mathrm{cm}}^2$, then find the value of $k$.

The area of the isosceles triangle whose each of the equal sides is $8 \mathrm{cm}$ and the base is $9 \mathrm{cm}$ is $k {\mathrm{cm}}^2$. Find the value of $k$ (correct up to $2$ decimal places)