The perimeter of a circle is known as its .

$10$ hectares $=$ _____ ${\mathrm{m}}^2$

The area of a circle of radius $1$$\mathrm{cm}$ is _____.

A rectangle is made with $18$ $\mathrm{m}$ long rope. The length of the rectangle is $5$ $\mathrm{m}$. If the breadth is $k \mathrm{m}$, find $k$.

If the area of a square is increased four times, how much does the perimeter increase?

If the area of a rectangle one side of which measures $12 \mathrm{m}$ and the diagonal measures $13 \mathrm{m}$ is $k {\mathrm{m}}^2$, find $k$.

A triangle with base $24 \mathrm{cm}$ and height $15 \mathrm{cm}$ is cut from a rectangle of length $40 \mathrm{cm}$ and breadth $24 \mathrm{cm}$. If the area of remaining piece is $k {\mathrm{cm}}^2$, find $k$.

The area of a parallelogram is $60 {\mathrm{cm}}^2$ and the base of the parallelogram is $12.5$ $\mathrm{cm}$. If its altitude is $h \mathrm{cm}$, find the value of $h$ in decimal.

The area of the portion $PQORSP$ is $k {\mathrm{cm}}^2$. Find $k$.