$A$ well,$20 \, m$ deep,is $7 \, m$ in radius. Find the cost of cementing the inner curved surface at the rate of ₹ $15$ per $m^2$. (in ₹)

Two solid spheres made of the same metal have weights $5920\, g$ and $740\, g$ respectively. Determine the radius of the larger sphere,if the diameter of the smaller one is $5\, cm$. (in $cm$)

The curved surface area of a cylinder is $1320 \, cm^2$. If its height is $30 \, cm$,find its diameter (in $cm$).

There are two boxes of metal sheet. The length,width,and height of a cuboidal box are $30 \, cm$,$25 \, cm$,and $20 \, cm$ respectively. $A$ cubical box has each edge of $25 \, cm$. Find out which box requires more metal sheet and by how many $cm^2$?

Find the curved surface area and the total surface area of a cone with radius $3.5 \, cm$ and height $12 \, cm$.

Find the curved surface area and the total surface area of a hemisphere with a radius of $2.1 \, m$.