The given figure shows $4$ identical quadrants in a square. If the area of the shaded part is  $k {\mathrm{cm}}^2$, then find the value of $k$.(Take $\mathrm{\pi }=3.14)$

A sheet of metal has dimensions $56 \mathrm{c}\mathrm{m}$ by $33 \mathrm{c}\mathrm{m}$. It is melted down and recast into discs of the same thickness and radius $7 \mathrm{c}\mathrm{m}$. How many discs will be cast?

The area of two equal circles in the figure is $308 \mathrm{c}{\mathrm{m}}^2$. Find the area of the rectangle in ${\mathrm{cm}}^2$.

The figure given alongside shows two identical semi-circles enclosed in a circle. The diameter of the circle is $28 \mathrm{c}\mathrm{m}$. The distance between the two semi-circles is $8 \mathrm{c}\mathrm{m}$. Find the area of the shaded part in ${\mathrm{cm}}^2$. $\left(\mathrm{T}\mathrm{a}\mathrm{k}\mathrm{e} \mathrm{\pi }=3.14\right)$

Two small circular parks of diameters $16 \mathrm{m}$ and $12 \mathrm{m}$ are to be replaced by a bigger circular park. If the radius of the new park is $R \mathrm{m}$ and if the new park occupies the same space as the two small parks, then find the value of $R$.

A rope by which a calf is tied is increased from $12 \mathrm{m}$ to $23 \mathrm{m}$. How much additional grassy ground shall it graze?