If a hemisphere is melted and four spheres of equal volume are made,the radius of each sphere will be equal to

The height of a right circular cone and the radius of its circular base are $9 \, cm$ and $3 \, cm$ respectively. The cone is cut by a plane parallel to its base so as to divide it into two parts. The volume of the frustum (i.e.,the lower part) of the cone is $44 \, cm^3$. The radius of the upper circular surface of the frustum $\left(\text{taking } \pi = \frac{22}{7}\right)$ is

$A$ right circular cylindrical tunnel of diameter $5\, m$ and length $10\, m$ is to be constructed from a sheet of iron. The area of iron sheet required will be..........$\pi\, m^2$.

The length of the diagonal of a cube is $6 \text{ cm}$. The volume of the cube (in $\text{cm}^3$) is (in $\sqrt{3}$)

$1496 \, cm^3$ of a metal is used to cast a pipe of length $28 \, cm$. If the internal radius of the pipe is $8 \, cm$,then the outer radius of the pipe is (in $cm$):

The curved surface area of a circular cylinder of height $h$ and the slant surface area of a cone of slant height $2h$,having the same circular base,are in the ratio of: