$A$ cylinder is closed at both the ends by hemispheres. The radius of the cylinder is $20 \, cm$ and the total height of the article is $80 \, cm$. Find the total surface area of this combined article. $(\pi = 3.14)$ (in $cm^2$)

$A$ right triangle,whose sides are $3\, cm$ and $4\, cm$ (other than the hypotenuse) is made to revolve about its hypotenuse. Find the surface area of the double cone so formed. (Use $\pi = 3.14$) (in $cm^2$)

The decorative block shown in the figure is made of two solids - a cube and a hemisphere. The base of the block is a cube with edge $5 \, cm$,and the hemisphere fixed on the top has a diameter of $4.2 \, cm$. Find the total surface area of the block. (in $cm^2$) (Take $\pi = \frac{22}{7}$)

Write 'True' or 'False' and justify your answer:
$A$ solid cylinder of radius $r$ and height $h$ is placed over another cylinder of the same height and radius. The total surface area of the shape so formed is $4 \pi r h + 4 \pi r^2$.

The base of a cone is in the shape of a ..............

An oil funnel made of a tin sheet consists of a $10 \, cm$ long cylindrical portion attached to a frustum of a cone. If the total height is $22 \, cm$,the diameter of the cylindrical portion is $8 \, cm$,and the diameter of the top of the funnel is $18 \, cm$,find the area of the tin sheet required to make the funnel.