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

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

The area of a circle is $75.46\, cm^{2}$. Find its circumference. (in $cm$)

The circumference of a circle is $176 \, cm$. Find its radius in $cm$.

In $\odot(O, 4)$,$\widehat{ACB}$ is a minor arc and $m \angle AOB = 45^\circ$. Then,the length of minor $\widehat{ACB}$ is $\ldots \ldots \ldots \ldots$

In a circle with radius $42 \ cm$,a minor arc subtends an angle of $60^{\circ}$ at the centre. Find the area of the minor sector and the minor segment corresponding to this arc. (Use $\sqrt{3} = 1.73$)