Find the circumference and the area of a circle with diameter $42 \, cm$.

The union of a chord of a circle and its corresponding arc is called $\ldots \ldots \ldots \ldots$

If the radius of a circle is increased by $10 \%,$ then the corresponding area of the new circle will be $\ldots \ldots \ldots . . .$

In a circle with radius $20\, cm$,the area of a sector formed by an arc of length $10\, cm$ is ............. $cm^2$.

The radius of a circular ground is $35 \, m$. Inside it,a $3.5 \, m$ broad road runs around its boundary. $A$ part of the road between two radii forming an angle of measure $72^{\circ}$ at the centre is to be repaired. Find the cost of repairing at the rate of ₹ $80 / m^{2}$. (in ₹)

If the radius of a circle is increased by $10 \%,$ its area will increase by $\ldots \ldots \ldots . \%$