In a circle with centre $O$,$\overline{OA}$ and $\overline{OB}$ are radii perpendicular to each other. The perimeter of the sector formed by these radii is $75 \, cm$. Find the area of the corresponding minor segment. (in $cm^2$)

In $\odot(O, r)$,$\overline{OA}$ and $\overline{OB}$ are two radii perpendicular to each other. If the perimeter of the minor sector formed by these radii is $20\,cm$,then $r = \ldots\,cm$.

The side length of square $ABCD$ shown in the diagram is $42 \ cm$. The shaded design is formed by drawing semicircles on all the sides of the square. Find the area of the shaded design in $cm^2$.

The length of the diagonals of a square garden $ABCD$ is $120\, m$. As shown in the figure,there are flower beds on two opposite sides of the garden in the shape of minor segments,the center of which is the point of intersection of the diagonals. Find the area of these flower beds. $(\pi=3.14)$ (in $m^2$)

The radius of a wheel of a car is $21 \, cm$. If it makes $800$ rotations per minute,find the speed of the car in $km/h$.

With respect to the given diagram,which of the following correctly matches the information in Part $I$ and Part $II$?

Part $I$	Part $II$
$1. \overline{OA} \cup \overline{OB} \cup \widehat{APB}$	$a. \text{Major sector}$
$2. \overline{AB} \cup \widehat{AQB}$	$b. \text{Minor segment}$
$3. \overline{AB} \cup \widehat{APB}$	$c. \text{Minor sector}$
$4. \overline{OA} \cup \overline{OB} \cup \widehat{AQB}$	$d. \text{Major segment}$