The circumference of a circular ground is $352\, m$. Find the area of the ground (in $m^2$).

The ratio of the radii of two circles is $4: 5$. Then,the ratio of their areas is...........

In a circle with radius $14 \, cm$,the area of the minor sector corresponding to minor $\widehat{ACB}$ is $77 \, cm^2$. Then,minor $\widehat{ACB}$ subtends an angle of measure $\dots$ at the centre. (in $^\circ$)

Two minor sectors of two distinct circles have the measure of the angle at the centre equal. If the ratio of their areas is $4:9,$ then the ratio of the radii of the circles is ........

The area of $\odot(O, r)$ is $240 \, cm^2$. In $\odot(O, r)$,minor arc $\widehat{ACB}$ subtends an angle of measure $45^\circ$ at the centre. Then,the area of minor sector $OACB$ is $\dots \dots \dots \, cm^2$.

The radii of two concentric circles are $23 \, cm$ and $16 \, cm$. Find the area of the circular ring formed by the circles (in $cm^2$).