An umbrella has $8$ ribs which are equally spaced. Assuming umbrella to be a flat circle of radius $45 \mathrm{cm}$. If the area between the two consecutive ribs of the umbrella is $k {\mathrm{cm}}^2$ then find $k$, correct upto one decimal place. [Assume $\mathrm{\pi }=\frac{22}{7}$]

 

The area of an equilateral triangle is $100\sqrt{3} {\mathrm{cm}}^2.$ Taking each vertex as the Centre, a circle is described with a radius equal to half the length of the side of the triangle, as shown in the figure. If the area of that part of the triangle which is not included in the circle is $k {\mathrm{cm}}^2$, then find $k$. (Take $\pi =3.14\text{ and }\sqrt{3}=1.732)$