The number of coins,each of radius $0.75\, cm$ and thickness $0.2\, cm$,to be melted to make a right circular cylinder of height $8\, cm$ and radius $3\, cm$ is:

Find out the amount of concrete required to erect a concrete pillar whose circular base has a perimeter of $8.8\, m$ and whose curved surface area is $17.6\, m^2$. $\left(\pi=\frac{22}{7}\right)$

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

$A$ right circular cone is $3.6 \ cm$ high and the radius of its base is $1.6 \ cm$. It is melted and recast into a right circular cone with a base radius of $1.2 \ cm$. The height of the new cone (in $cm$) is:

If each edge of a cube is increased by $50 \%$,the percentage increase in surface area is (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