In a quadrilateral $ABCD$,the sides $AB, BC, CD, DA$ measure $20\, m, 13\, m, 17\, m$ and $10\, m$ respectively,and the diagonal $AC$ is $21\, m$. The area of the quadrilateral is ........ $m^2$.

The length and breadth of a rectangle are increased by $10 \%$ and $20 \%$ respectively. What will be the percentage increase in the area of the rectangle (in $\%$)?

$A$ $2 \text{ m}$ broad pathway is to be constructed around a rectangular plot on the inside. The area of the plot is $96 \text{ m}^2$. The rate of construction is $₹ 50 / \text{ m}^2$. Find the total cost of construction (in $₹$).

$A$ cow is tied by a rope at the corner of a rectangular field. If the length of the rope is $14\, m$,then the area of the field which the cow could graze is.......$m^2$

In a swimming pool measuring $90\, m$ by $40\, m$,$150$ men take a dip. If the average displacement of water by a man is $8\, m^3$,what will be the rise in water level? (in $cm$)

Height of an equilateral triangle is $6 \, cm$. Find its side? (in $cm$)