The number of marble slabs of size $20 \text{ cm} \times 30 \text{ cm}$ required to pave the floor of a square room of side $3 \text{ m}$ is:

If the two diagonals of a parallelogram are $72 \, cm$ and $30 \, cm$ respectively,then find its perimeter in $cm$.

An oblong piece of ground measures $19$ $meters$ $2.5$ $dm$ by $12$ $meters$ $5$ $dm$. From the centre of each side,a path $2$ $meters$ wide goes across to the centre of the opposite side. Find the cost of paving these paths at the rate of $Rs.$ $12.32$ per $sq$ $meter$. (in $Rs.$)

In measuring the sides of a rectangle,one side is taken $5 \%$ in excess,and the other $4 \%$ in deficit. Find the error percent in the area calculated from these measurements. (in $\%$)

On decreasing each side of an equilateral triangle by $2\, cm$,there is a decrease of $4\sqrt{3}\, cm^2$ in its area. The length of each side of the triangle is.........$cm$.

In the figure,$DE \parallel BC$. If $DE = 3 \text{ cm}$,$BC = 6 \text{ cm}$,and the area of $\Delta ADE = 15 \text{ cm}^2$,then the area of $\Delta ABC$ is ............ $\text{cm}^2$.