The diameters of two concentric circles are $8\, cm$ and $10\, cm$. The area of the region between them is

If the area of a square is $50$ $sq$ units,then the area of the circle drawn on its diagonal is

The area of a sector of a circle of radius $5 \, cm$,formed by an arc of length $3.5 \, cm$,is (in $cm^2$)

The area of a square field is $6050\, m^2$. How much time will it take to reach from one of its corners to the opposite corner at the rate of $10\, m$ in every $30$ seconds?

In trapezium $ABCD$,$AB || CD$ and $AB = 2 \, CD$. Its diagonals intersect at $O$. If the area of $\Delta AOB = 84 \, cm^2$,then the area of $\Delta COD$ is equal to (in $cm^2$)

Find the length of a rope by which a cow must be tethered in order that it may be able to graze an area of $9856 \, m^{2}$. (in $m$)