EM-774

Volume and surface area of solids

E Math · Secondary 3 · Hard · Volume and surface area of solids

A solid is made of a cylinder of radius

r

cm and height

r+4

cm, with a hemisphere of radius

r

cm attached on top. The flat circular base of the cylinder is on the table.

Which expression gives the total external surface area of the solid, in terms of

\pi

and

r

?
(Exclude the area of the base on the table.)

$4\pi r^2 + 8\pi r$
$2\pi r^2 + 8\pi r$
$4\pi r^2 + 4\pi r$
$6\pi r^2 + 8\pi r$

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