$A$ brick measures $20 \, cm$ by $10 \, cm$ by $7.5 \, cm$. How many bricks will be required to construct a wall $25 \, m$ long,$2 \, m$ high,and $0.75 \, m$ thick?

If the radius of a sphere is doubled,then its volume is increased by (in $\%$)

$A$ large solid sphere is melted and moulded to form identical right circular cones with base radius and height same as the radius of the sphere. One of these cones is melted and moulded to form a smaller solid sphere. Then the ratio of the surface area of the smaller to the surface area of the larger sphere is

The total number of spherical bullets,each of diameter $5$ decimetre,that can be made by utilizing the maximum of a rectangular block of lead with $11$ $m$ length,$10$ $m$ breadth and $5$ $m$ width is (assume that $\pi > 3$)

$A$ cylindrical tower is $5 \, m$ in diameter and $14 \, m$ high. The cost of white washing its curved surface at $50$ paise per $m^{2}$ is (in $Rs.$)

If the radius of a sphere is doubled,then its surface area is increased by (in $\%$)