The circumference of a circle is $251.2 \, cm$. Find its diameter. $(\pi = 3.14)$ (in $cm$)

The diagram below is formed by three semicircles. If $OA = OB = 70\, cm,$ find the area of the figure formed (in $cm^2$).

The maximum area of a triangle inscribed in a semicircle having radius $10 \, cm$ is $\ldots \ldots \ldots \, cm^2$.

In $\odot(O, r)$,minor arc $\widehat{ABC}$ subtends a right angle at the centre. The area of the minor segment formed by $\widehat{ABC}$ is $14.25\,cm^2$ and the area of $\Delta OAC$ is $25\,cm^2$. Then,the area of the minor sector formed by $\widehat{ABC}$ is $\ldots \ldots \ldots cm^2$.

The radius of a wheel of a car is $21 \, cm$. If it makes $800$ rotations per minute,find the speed of the car in $km/h$.

Is the area of the circle inscribed in a square of side $a \, cm$ equal to $\pi a^2 \, cm^2$? Give reasons for your answer.