As shown in the diagram, $\overline{ AC }$ is a diameter of the circle with centre O. $\Delta ABC$ is inscribed in a semicircle of the circle. If $AC =35 \,cm$, $AB =21\, cm$ and $BC =28\, cm ,$ find the area of the shaded region. (in $cm^2$)

In a circle with radius $30\,cm ,$ a minor arc subtends an angle of measure $60$ at the centre. Then, the area of the minor sector formed by that arc is $\ldots \ldots \ldots \ldots$ $cm ^{2}$.   $(\pi=3.14)$

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

The circumference of a circular ground is $220\, m .$ Outside it, runs a road of equal width. If the circumference of the ground with the road is $264\, m$, find the width of the road. (in $m$)

The circumference of the wheels of a truck is $440\, cm .$ They make $250$ rotations per minute. Then, the speed of the truck is $\ldots \ldots \ldots \ldots km / h$.

Find the area of the shaded field shown in $Fig.$