If a regular hexagon is inscribed in a circle of radius $r,$ then its perimeter is........$r$.

The area of a triangle is $216 \, cm^{2}$ and its sides are in the ratio $3:4:5$. The perimeter of the triangle is ....... $cm$.

$A$ room $5\, m \times 8\, m$ is to be carpeted leaving a margin of $10\, cm$ from each wall. If the cost of the carpet is ₹ $18$ per $m^2$,then the cost of carpeting the room will be (in $Rs.$)

If the ratio of areas of two circles is $4:9,$ then the ratio of their circumferences will be

If the area of a triangle whose base is $6\, cm$ is equal to the area of a circle of radius $6\, cm$,then find the height of this triangle (in $cm$).

The perimeter of a square is double the perimeter of a rectangle. The area of the rectangle is $240 \, cm^2$. What is the area of the square? (in $cm^2$)