A car travels $1$ kilometre distance in which each wheel makes $450$ complete revolutions. Find the radius of the its wheels.

An archery target has three regions formed by three concentric circles as shown in figure If the diameters of the concentric circles are in the ratios $1 : 2 : 3$, then find the ratio of the areas of three regions

The wheel of a motorcycle is of radius $35 \mathrm{cm}$. How many revolutions per minute must the wheel make to keep a speed of $66 \mathrm{km}/\mathrm{h}$.

A circular park is surrounded by a road $21 \mathrm{m}$ wide. If the radius of the park is $105 \mathrm{m}$, find the area of the road.

A square of diagonal $8 \mathrm{cm}$ is inscribed in a circle. Find the area of the region lying outside the circle and inside the square.

Note: Incorrect question in the book [inside the circle and outside the square] 

A path of $4 \mathrm{m}$ width runs round a semi-circular grassy plot whose circumference is $163+\frac{3}{7} \mathrm{m}$. Find cost of graveling the path at the rate of $₹1.50$ per $\mathrm{sq}. \mathrm{m}$