Water flows into a tank with a base of $150\, m \times 100\, m$ through a pipe with a cross-section of $2\, dm \times 1.5\, dm$ at a speed of $15\, km/h$. In what time will the water reach a depth of $3\, m$? (in $hours$)

The ratio of the curved surface area and volume of a cylinder is $1:7$. The ratio of the total surface area and volume is $187:770$. What is the ratio of its base radius to its height?

If $h, c, v$ are respectively the height,curved surface area,and volume of a right circular cone,then the value of $3 \pi v h^{3} - c^{2} h^{2} + 9 v^{2}$ is

Water is flowing at the rate of $5 \text{ km/h}$ through a pipe of diameter $14 \text{ cm}$ into a rectangular tank which is $50 \text{ m}$ long and $44 \text{ m}$ wide. The time taken,in hours,for the rise in the level of water in the tank to be $7 \text{ cm}$ is:

The height of a wall is six times its width,and the length of the wall is seven times its height. If the volume of the wall is $16128 \, m^3$,its width is ...... $m$.

The radii of two solid iron spheres are $1 \, cm$ and $6 \, cm$ respectively. $A$ hollow sphere is made by melting the two spheres. If the external radius of the hollow sphere is $9 \, cm$,then its thickness (in $cm$) is