The circumference of a circle with radius $8.4\,cm$ is $\ldots \ldots \ldots \ldots cm$.

The diameters of front and rear wheels of a tractor are $80 \,cm$ and $2 \,m$ respectively. Find the number of revolutions that the rear wheel will make in covering a distance in which the front wheel makes $1400$ revolutions.

Area of a sector of a circle of radius $36 \, cm$ is $54 \pi \, cm^{2}$. Find the length of the corresponding arc of the sector (in $cm$). (in $\pi$)

Areas of two circles are equal. Is it necessary that their circumferences are equal? Why?

If the perimeter of a circle is equal to that of a square,then the ratio of their areas is

The length of a diagonal of a square inscribed in a circle with radius $10\, cm$ is $\ldots \ldots \ldots . cm$.