The area of a ring whose outer and inner radii are respectively $20 \, cm$ and $15 \, cm$ is? (in $cm^2$)

$A$ cow is tied by a rope at the corner of a rectangular field. If the length of the rope is $14\, m$,then the area of the field which the cow could graze is.......$m^2$

$A$ hemispherical bowl of internal diameter $54 \ cm$ contains a liquid. The liquid is to be filled in cylindrical bottles of radius $3 \ cm$ and height $9 \ cm$. How many bottles are required to empty the bowl?

What is the radius of a circle,to the nearest $cm$,whose area is equal to the sum of the areas of the three circles of radii $22\, cm$,$19\, cm$,and $8\, cm$ respectively? (in $cm$)

$2$ poles of heights $15\, m$ and $30\, m$ stand upright on a playground. If their feet are $36\, m$ apart,find the distance between their tops in meters.

If the length of one side and the diagonal of a rectangle are $7 \text{ cm}$ and $25 \text{ cm}$ respectively,then find its perimeter (in $\text{cm}$).