If the radius of a circle is doubled, its area becomes $\ldots \ldots \ldots .$ times the area of the original circle.

A field is in the shape of an equilateral triangle in which the length of each side is $70\, m$. A cow is tethered at one of its vertices by a $5 \,m$ long rope. Find the area of the region in the field in which the cow can graze. $(\pi=3.14)$ (in $m^2$)

The length of the minute hand of a clock is $10.5 \,cm .$ The area of the region swept by it in $20$ minutes is $\ldots \ldots \ldots . . cm ^{2}$.

The cost of erecting wall all around a circular ground at the rate of ₹ $60 / m$ comes to be ₹ $26.400 .$ Find the cost of levelling the ground at the rate of ₹ $50 / m ^{2}$. (in ₹)

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 $\odot( O , r) \overline{ OA }$ and $ \overline{ OB }$ are two radii perpendicular to each other. If the, perimeter of the minor sector formed by those radii is $20\,cm ,$ then $r=\ldots \ldots \ldots . . . cm$