If the area of a circle is $49\pi$ square units, then its perimeter is 

In the figure, $ABCD$ is a square of side $14 cm. A, B, C \& D$ are the canters of four congruent circles such that each circle touches extremely two of the remaining three circles. If the area of the shaded region is $k c{m}^2$ then find the value of $k$.

The length of a rectangle field is $3$ times its breadth. If the area of the field is $147 sq.m,$ find its length and breadth.

$AB \mathrm{and} CD$ are the arcs of two concentric circles with centre $O$ of radius $21 \mathrm{cm}$ and $7 \mathrm{cm}$ respectively. If $\angle AOB=30°$ as shown in the figure, find the area of the shaded region.

In the figure, $ABCD$ is a square, and two semicircles touch each other externally at $P$. The length of each semicircular arc is equal to $11 \mathrm{cm}$. Find the area of the shaded region.