In a cylinder,if the radius is doubled and the height is halved,the curved surface area will be:

The inner diameter of a cylindrical wooden pipe is $24 \, cm$ and its outer diameter is $28 \, cm$. The length of the pipe is $35 \, cm$. Find the mass of the pipe,if $1 \, cm^3$ of wood has a mass of $0.6 \, g$. (in $, kg$)

Write True or False and justify your answer in each of the following:
The volume of the largest right circular cone that can be fitted in a cube whose edge is $2r$ is equal to the volume of a hemisphere of radius $r$.

The ratio of the radius and slant height of a cone is $3:5$ and its curved surface area is $423.9 \, cm^2$. Find its volume. $(\pi = 3.14)$ (in $cm^3$)

$A$ child is playing with building blocks, which are in the shape of cubes, and has built a structure as shown in the figure. If the edge of each cube is $3 \, cm$, find the volume of the structure built by the child. (in $cm^3$)

The dimensions of each iron hollow box are $30 \, cm \times 15 \, cm \times 10 \, cm$. What is the volume of a carton containing $60$ such boxes? (in $m^3$)