The wheel of a motorcycle has a radius of $35 \, cm$. How many revolutions per minute must the wheel make to maintain a speed of $66 \, km/h$?

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

The ratio of the areas of two circles is $25: 36$. Then,the ratio of their circumferences is:

Find the area of the shaded region in the figure where arcs drawn with centers $A, B, C,$ and $D$ intersect in pairs at mid-points $P, Q, R,$ and $S$ of the sides $AB, BC, CD,$ and $DA,$ respectively of a square $ABCD$ (Use $\pi = 3.14$) (in $cm^{2}$).

The area of a minor sector of $\odot(P, 30)$ is $300 \, cm^2$. The length of the arc corresponding to it is .......... $cm$.

The length of a minor arc of $\odot(O, 7)$ can be $\ldots \ldots \ldots \ldots$ units.