Exercise

What is the shape of a sphere and find the surface area of a sphere whose radius is $7$ units.

The external radius of a hollow sphere made of $1 cm$ thick lead sheet is $6 cm$. By melting the sphere, a solid cylindrical rod of $2 cm$ radius is formed. What is the length of the rod ?
 

The volume of a hollow cylinder is $440 {\mathrm{cm}}^3$. The inner radius of the cylinder is $5 \mathrm{cm}$ and the height of the hollow cylinder is $14 \mathrm{cm}$. Find the outer radius of the cylinder.

The external and internal radius of a hollow tube in the form of a right circular cylinder are $5 \mathrm{cm}$ and $4 \mathrm{cm}$. If the area of whole surface of the tube is $1188 \mathrm{sq}.\mathrm{cm}$, what is the length of the tube?

Find the volume of a hollow cylinder having inner radius $4 \mathrm{m}$, outer radius $6 \mathrm{m}$ and height $14 \mathrm{m}$.

The volume of a hollow cylinder is $880 {\mathrm{cm}}^3$. The inner radius of the cylinder is  $4 \mathrm{cm}$ and outer radius of the cylinder is $6 \mathrm{cm}$. Find the height of the hollow cylinder.

The outer radius of the cylinder is $4 \mathrm{m}$ and the height of the hollow cylinder is $7 \mathrm{m}$. The volume of a hollow cylinder is $220 {\mathrm{m}}^2$. Find the inner radius of the cylinder.

Water in a cylindrical tank of a diameter $4 \mathrm{m}$ and height $10 \mathrm{m}$ is released through a cylindrical pipe of diameter $10 \mathrm{cm}$ at the rate of $2.5 \mathrm{km}/\mathrm{hr}$. How much time will it take to empty the half of the tank? Assume that the tank is full of water to begin with.