The cross-section of a canal is a trapezium in shape. If the canal is $10 \mathrm{m}$ wide at the top $6 \mathrm{m}$ wide at the bottom and the area of cross-section is $72 {\mathrm{m}}^2$ determine its depth. If the depth is $A \mathrm{m}$ then find $A$.

Mohan wants to buy a trapezium shaped field. Its side along the river is parallel and twice the side along the road. If the area of this field is $10500 {\mathrm{m}}^2$ and the perpendicular distance between the two parallel sides is $100 \mathrm{m}$, If the length of the side along the river is $x \mathrm{m}$, then find the value of $x$.

In the given figure, a parallelogram is drawn in a trapezium, the area of the parallelogram is $80 {\mathrm{cm}}^2$. If the area of the trapezium is $k {\mathrm{cm}}^2$, find the value of $k$.