The dome of a building is in the form of a hemisphere. Its radius is $4.2 \, m$. Find the cost of painting it at the rate of ₹ $18$ per $m^2$. (in ₹)

The total surface area of a cone whose radius is $\frac{r}{2}$ and slant height is $2l$ is

The length,breadth,and height of a cuboidal box are $30 \, cm$,$20 \, cm$,and $8 \, cm$ respectively. Find the lateral surface area of the cuboidal box (in $cm^2$).

The diameters of two spheres are in the ratio $3: 5$. What is the ratio of their volumes?

The total surface area of a cube is $864 \, cm^2$. Then its edge is $\ldots \ldots \ldots \, cm$.

The thickness of a metallic tube is $5 \, mm$ and the inner diameter of the tube is $10 \, cm$. Find the mass of a $70 \, cm$ long tube,if the density of the metal is $8 \, g/cm^3$. (in $g$)