AM-1468

Quadratic models

A Math · Secondary 4 · Medium · Quadratic models

A solid cylinder has radius

r

cm and height

h

cm. Its total surface area is fixed at

80\pi\,\text{cm}^2

. The total surface area is given by

2\pi r^2+2\pi rh=80\pi

. Express

h

in terms of

r

.

$h=\dfrac{40-r^2}{r}$
$h=\dfrac{40-3r^2}{r}$
$h=\dfrac{40}{r}-2r$
$h=\dfrac{80-r^2}{2r}$

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