The sides of a triangle are in the ratio $3:4:5$. If its perimeter is $36 \text{ cm}$,then the area of the triangle is ...... $\text{cm}^2$.

The sum of all interior angles of a regular polygon is twice the sum of all its exterior angles. The number of sides of the polygon is

$A$ tank is $25 \ m$ long,$12 \ m$ wide and $6 \ m$ deep. The cost of plastering its walls and bottom at $75 \ paise/m^2$ is (in $Rs.$)

The radius of a coin is $1\, cm$. If four of these coins are placed on a table so that the rim of each touches that of the other two,find the area of the unoccupied space between them. (in $cm^2$)

$A$ rectangle has width $a$ and length $b$. If the width is decreased by $20 \%$ and the length is increased by $10 \%$,what is the area of the new rectangle as a percentage of the original area $ab$?

If the altitude of an equilateral triangle is $12 \sqrt{3} \text{ cm}$,then its area would be