The ratio of the radii of two circles is $4:5$. Find the ratio of their areas.

A rectangular ground is $90 \mathrm{m}$ long and $32 \mathrm{m}$ broad. In the middle of the ground, there is a circular tank of radius $14 \mathrm{metres}$. Find the cost of turfing the remaining portion at the rate of $₹50 \mathrm{per} \mathrm{square} \mathrm{metre}$.

In the given figure, four equal circles are described about the four corners of a square so that each circle touches two of the circle as shown in the figure. Find the area of the shaded region, each side of the square measuring $14 \mathrm{cm}$. (Use $\mathrm{\pi }=\frac{22}{7}$)

A horse is tethered to one corner of a rectangular field, $60 \mathrm{m} \text{by} 40 \mathrm{m}$, by a rope $14 \mathrm{m}$ long. On how much area can the horse graze? (Use $\mathrm{\pi }=\frac{22}{7}$)

In the given figure, a circle of diameter $21 \mathrm{cm}$ is given. Inside this circle, two circles with diameters $\frac{2}{3}$ and $\frac{1}{3}$ of the diameter of the big circle have been drawn, as shown in the given figure. Find the area of the shaded region.