$A$ metallic sphere with radius $18 \,cm$ is melted and recast to produce cylinders with radius $3 \,cm$ and height $12 \,cm$. Find the number of cylinders produced.

Total surface area of a cone exceeds its curved surface area by $\ldots \ldots \ldots . . .$

The area of the circular base of a hemisphere is $154 \, cm^{2}$. Then,its total surface area is $\ldots \ldots \ldots \, cm^{2}$.

$A$ cylinder is closed at both the ends by $28 \, cm$ high cones. The radius and the height of the cylinder are $21 \, cm$ and $50 \, cm$ respectively. Find the total surface area of the article in $cm^2$.

Twelve solid spheres of the same size are made by melting a solid metallic cylinder of base diameter $2 \, cm$ and height $16 \, cm$. The diameter of each sphere is (in $cm$):

The area of the base of a cylinder is $20 \, cm^{2}$ and its height is $5 \, cm$. Then,its volume is $\ldots \ldots \ldots \, cm^{3}$.